SOIL VAPOR SAMPLING PROCEDURES

R-009-205.5

3959

SOIL VAPOR SAMPLING PROCEDURES

12/14/92

DOE-F'N/EPA yK'3 ENCLOSURE

Enclosure

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3959 - OPERATING AND SERVICE MANUAL

for

CENTURY SYSTEMS'

Portable Organic Vapor Analyzer (OVA)

and Optional Accessorles Model OVA-128

REVISION C

Analabs A Unit of Foxboro Analytical 80 Republic Drive. North Haven, Connecticut 06473 U.S.A.

ekphone: (203) 288-8463 T ~ C X 96-3518

TABLE OF CONTENTS PAGE

1: Oexrlptlon and Leading PaNculars ............................................................... 1 General ........... I ................................................................................ 1

1.2 1.3 1.4 1.5 1.5.1 1.5.2 1.5.3 1.5.4 1 s.5 1.6

Typical Applications ................................................................................. 1 Other Typical Uses ........... i ...................................................................... 1 Major Features .................................................................................... - 1 Adaptability Features and Standard Accessories ...................................................... 2 General ............................................................................................ 2 Probe .............................................................................................. 2 Particle Filters ...................................................................................... 2 Instrument Carrying Case ........................................................................... 2 Mobile Installation ................................................................................. - 2 SpeciHcations ...................................................................................... 2

SECTION 2: Detailed Operating Procedures ................................................................... - 2 2.1 General ............................................................................................. 2

’ 2.2 System Controls . Indicators and Connectors .......................................................... 4 2.3 Starting Procedure ................................................................................. - 4 2.3.1 Initial Preparation for Use ........................................................................... - 4 2.3.1.1 Initial Assembly 4 2.3.1.2 Servicing ........................................................................................... 4 2.3.1.3 Safety Precautions 5 2.3.2 Turn On Procedure .................................................................................. 5 2.4 Operating Procedures ............................................................................... 5 2.5 Shut Down Procedure ............................................................................... 6

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2.6 Fuel Refilling ............................................................. 2.7 Battery Recharging - AC Battery Charger .................................. 2.7.2 %Charger ............................ ................................... 2.8 Charcoal Filtering ........................................................ 2.9 Moisture Filtering ........................................................

SECTION 3: Summarized Operatlng Procedures ..................................... 3.1 General ................................................................. 3.2 Startup .................................................................

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.......................... 7 - 3.3 Shut Down ...........................................................................................

SECTION 4: Callbratlon ........................................................................................ 7 4.1 General ............................................................................................ 7 4.2 Electronic Adjustments ............................................................................. 8 4.2.1 Gain Adjustment ................................................................................... - 8 4.2.2 Bias Adjustment .................................................................................... 8 4.3 Calibration to Other Organic Vapors .................................................................. 8 4.3.1 Setting Gas Select Control (Span) .................................................................... 8 4.3.2 Using Empirical Data ................................................................................ 8 4.3.3 Preparation of Calibration Standards ................................................................ - 8 4.3.3.1 Commercial Samples ................................................................................ 8 4.3.3.2 Pure Gaseous Samples ............................................................................. - 8 4.3.3.3 Gaseous and Liquid Samples (Alternate Method) ...................................................... 9 4.4 Theory ............................................................................................ - 9 4.4.1 Hydrocarbons ..................................................................................... - 9 4.4.2 Other Organic Compounds .......................................................................... 9

SECTION 5: Safety Considerattons .......................................................................... -11 General ........................................................................................... 11

5.2 Operating . Servicing and Modifying ................................................................ 11 5.3 Electrical Protection ............................................................................... 11

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5.4 5.5 5.6 5.7 5.8

3959 * Fuel Supply and Tank .............................................................................. 11 Hz flow Restrictom ................................................................................ 11 Detector Chamber ................................................................................ -11 H2 Filling and Emptying Operations .................................................................. 11 Venting .......................................................................................... -11

SECTlON.6: Malntenance .................................................................................... 13 6.1 6.2 6.2.1 6.2.1.1 6.2.1.2 6.2.1.3 6.2.1.4 6.22 6.2.3 6.2.3.1 6.2.3.2 6.2.4 6.2.4.1 6.2.4.2 6.2.4.3 6.2.5 6.2.5.1 6.2.5.2 6.2.6 6.3 6.4 6.5 6.6

General ........................................................................................... 13 Routine Maintenance .............................................................................. 13 Filters ............................................................................................. -13 Primary Filter ..................................................................................... -13 Particle Filters .................................................................................... -14 MixerlBurner Assembly Filter ..................................................................... -14 Exhaust flame Arrestor ........................................................................... -14 Pickup Fixtures .................................................................................... -14 Seal Maintenance - Cylinder Assembly ............................................................ -14 H2 Tank. H2 Supply and Refill Valves ................................................................. 14 Refiller Valve Packing Adjustmen$ ................................................................. -14 Air Sampling System Maintenance .................................................................. -15 General ........................................................................................... 15 Testing for Leaks ................................................................................... 15 Leak Isolation ...................................................................................... 15 Contamination Control and Maintenance ............................................................ 15 General ........................................................................................... 15 Analysis and Correction ........................................................................... -16 Fuse Replacement ................................................................................. 17 Trouble Shooting ................................................................................. -17 Factory Maintenance ............................................................................... 17 Field Maintenance ................................................................................ -18 Recommended Spares ................ : ............................................................ 18

SECTION 7: Optlonal Accessories ............................................................................ -23 7.1 7.1.1 7.1.2 7.1.2.1 7.1.22 7.1.3 - . ? <

. . a . 2.L I . . u . I . . . 7.7.3.3 7.1.3.4 7.1.3.5 7.1.4 7.1.4.1 7.1.4.2 7.1.4.3 7.1 -4.4 7.1.5 7.1.5.1 7.1 S.2 7.1 -5.3 7.1.5.4 7.2 7.2.1 7.2.2 7.23 7.24 7.25 7.2.6 7.26.1 7.2.6.2

Gas Chromatograph (GC) Option ..................................................................... - 2 3

Description and Leading Particulars ................................................................. 23 Introduction ....................................................................................... 23

General ........................................................................................... 23 Principle of Operation .............................................................................. 23 Operating Procedures ............................................................................. - 2 8 ..- ..-. c . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28

2 2 . G- Sj-.-;.;i -iii;css .Z nd Ck..++~i.i=..,.; ............................................................... Servicing and Turn On ............................................................................... 29 Survey Mode Operation ........................................................................... -29 GC Mode Operation ................................................................................ -29 Calibration i ....................................................................................... 29

Technical Discussion .............................................................................. 29

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General ........................................................................................... 29

Preparation of Calibration Samples ................................................................. -32 Calibration Data ................................................................................... -32 Maintenance ...................................................................................... 32 General .......................................................................................... -32 Routine Maintenance ............................................................................. -32 Trouble Shooting ................................................................................. - 3 5 Recommended Spares ............................................................................. 35 Recorder Option ................................................................................... 37 General ........................................................................................... 37 Applications ...................................................................................... -37 Features ............................................................................................ 37 Controls and Connections .......................................................................... 37 operating Procedures ............................................................................ ?.- 37 Calibration ........................................................................................ 37 General .......................................................................................... -37

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MechanicalZero Adjustment .............................................................. 37 r- .. '

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7.26.3 7.2.7

w n Adlustment.. .......................................................................... : ...... 37 safety.. ....................................... i.. __ ................................................ --- -- - -

and-Routlne Operations .............................................................. -38 -37 ... -- - -7;2;8 Mafit@-

7.2.8.1 . Changing Chart Speeds ........................................................................... .38 7.3 Activated Charcoal Fllter Assembly ................................................................ -38 7.4 OVA Sample Dilutor.. ............................................................................. -38 7.4.1 Setting Dilution Rate .............................................................................. .3!3 7.5 OVA Septum Adapter. ............................................................................. .39

APPENDIX A: Sample Forms, A ~ I c a ~ / T ~ Notes, Sct.amatlc. Omwings. Parts Usts

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CENTURY SYSTEMS CORPORATION EO. BOX 818 I ARKANSAS C m . KANSAS 67005 I 3 1 6 4 4 7 4 3 1 1 I Twx 91Q-740-6740

SECTlON 1 OESCRIPllON AND LEADING PARTICULARS 1.1 GENERAL

The Century Portable Organic Vapor Analyzer (OVA). illustrated in Figure 1-1. is designed to detect and measure hazardous gases found in almost all industries. It has broad application, since it has a chemically resistant sampling system and can be calibrated to almost all organic vapors. It is extremely sensitive and can provide accurate indication of gas concentration in one of three ranges: 0 to 1 0 ppm; 0 to 100 ppm; and 0 to 1,OOO ppm. While designed as a lightweight portable instrument, i t can readily be adapted to remote monitoring applications.

The instrument utilizes the principle of hydrogen flame ionization for detection and measurement of organic vapors. The instrument measures organic vapor concentration by producing a response to an unknown sample, which can be related to a gas of known com- position to which the instrument has previously been calibrated. During normal survey mode operation, a continuous sample is drawn into the probe and transmitted to the detector chamber by an internal pum- ping system. The sample flow rate is metered and passed through particle filters before reaching the detector c,ka--”a- I - - - - . -= .=-.-, exDosec: to E hyc:ogen flame whtch ionizes the organlc vapors. Wnen most organic vapors burn, they leave positively charged carboncontaining ions which are collected by a negative collecting electrode in the chamber. An electric field exists between the con- ductors surrounding the flame and the collecting electrode which drives the ions to the collecting electrode. As the positive ions are collected. a current corresponding to the collection rate is generated on the input electrode. This current is measured with a linear elec- trometer preamplifier which has an output signal proportional to the ionization current. A signal conditioning amplifier is used to amplify the signal from the preamp and to condition it for subsequent meter or external recorder display. The meter display is an integral part of the ProbelReadout Assembly and has a scale from 0 to 10.

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TYPICAL APPLICATIONS Measurement of most toxic organic vapors present in industry for compliance with Occupa- tional Safety and Health Administration (OSHA) requirements. Process monitoring and evaluation. Evaluation and monitoring applications in the air pollution field. Leak detection in storage, transportation and handling equipment. Survey of gas distribution and transmission lines and equipment for compliance with Office of Pipeline Safety (OPS) requirements. Forensic science applications.

OTHER TYPlCAL USES Controlling and monitoring atmospheres in manufacturing and packaging operations. ‘ Mudlogging, gas and mineral exploration. Leak detection related to volatile fuel handling equipment.

MAJOR FEATURES basic instrument consists of two maior

assemblies, the ProbelReadout Assembly and the Side Pack Assembly (see Figure 1-1). The recorder is op- t:=n;! cn 2 : : m3<clc, 5 ~ : is r.=rc-~~.!!)~ us& v:?? E!! i-- s;ruments which incorpor2:e the GC Option. The 0utp-k meter ana alarm level adjustments are incorpora:ed in the ProbelReadout Assembly which is operated with one hand. The Side Pack Assembly contains the remaining operating controls and indicators, the electronic circuitry, detector chamber, hydrogen fuel supply and electrical power supply. It is a quantitative type instrument with sensitivity to 0.1 ppm methane.

Other major features are: 250. linear scale readout. less than two second response time and minimum eight hour service life for fuel supply and battery pack. A battery test feature allows charge condition to be read on the meter. Hydrogen flameout is signified by an audi-‘.. ble alarm plus a visual indication on the meter. The instrument contains a frequency modulated detection alarm which can be preset to sound at a desired concentration level. The frequency of the detwtion alarm

3959:. . varies as a function of detected level giving an audible indication of organic vapor concentration, -e .instrul merit is designkd forone man. one hand operation and the entire unit weighs a total of less than 12 pounds, including fuel supply and battery. An earphone is provided for "only operator" monitoring.

During use, the Side Pack Assembly can be carried by the operator on either his left or right side or as a back pack. The Side Pack Assembly is housed in a high impact plastic case and weighs less than 10 pounds. The ProbelReadout Assembly can be detached from the Side Pack Assembly and broken down for transport and storage. See Figure 1-2 for the breakdown capability of the instrument.

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1.5 _ADAPTABILIlY FEATURES AND STANDARD

1.5.1 GENERAL Maximum flexibility and operability features are in-

cluded in the instrument design. As shown in Figure 1-2, a variety of pickup fixtures can be used. They can be installed by simply turning a knurled locking nut. Small diameter tubing can be used for remote sampling and electrically insulated flexible extensions can be used for difficult places to reach.

ACCESSORIES

1.5.2 PROBE The telescoping probe allows the length to be in-

creased or decreased over an eight inch range to suit the individual user. A knurled locking nut is used to lock the probe at the desired length. The probe is attached to the Readout Assembly using a knurled locking nut. For measurements in close areas, the probe is replaced with a Close Area Sampler, which is supplied as a Stan- dard accessory.

1.5.3 PARTICLE FILTERS m e primary filter is of porous stainless and located

behind the sample inlet connector, see Side Pack Assembly drawing in Appendix "A". In addition, replaceable porous metal filters are installed in the "close area" sampler, the pickup funnel and the tubular sampler. 1.5.4 I N S T R U M E N T C A T R Y I N G CASE

An instrument carrying case is provided to transport, ship and store the disassembled ProbelReadout Assembly, the Side Pack Assembly and other standard equipment.

1.5.5 MOBILE INSTALLATION The instrument is readily adaptable to a mobile ap-

plication by simply plugging into vehicle power and hydrogen fuel supply and making provisions for drawing sample from the vehicle primary sampling system.

1.6 SPECIFICATIONS Sensltlvlty: 0.1 ppm (methane) Response Ume: Less than 2 seconds Readout 0 to 10 ppin, 0 to 100 ppm, 0 to 1 .ooO ppm,

2500 linear scaled meter; external monitor connector

.. .s I Sample flow ram. Nominally 2 units

Fuel- sum Z-cuMc centimeter tank of p ire. hydrogen at maximum pressure of 2300 FSG, fillable while in case

Prlmary electrical powec Rechargeable ind replaceable battery pack at 12VDC

Servlce life: Hydrogen supply and battery power+ hours Operating time minimum

Sire: Standard Unlt 8518 x 11438 x 4-1/4 Id Unlt 8-518 x 11-5/8 x 4-1 12 Probe/Reac;out

Weight: Standard Unlt Side Pack Assembly. less than 10 lbs. FM Unlt: Side Pack Assembly, less than 11 Ibs. ProbelReadout Assembly: less than 2 Ibs.

Operator requirements: One man. one hand operation

Detection alarm: Frequency modulated audible alarm. Can be preset to desired level. Fre- quency varies as a function of detection level

Flameout Indlcatlon: Audible alarm plus visual meter indication

Battery test Battery charge condition indicated on readout meter or battery recharger

Plckup fixtures: Variety of types for various applications

Probe: Telescoping adjustment over 8 inches or probe can be completely removed from Readout Assembly

Umbllical cord: Cable between readout and sidepack with connectors for electrical cable and sample hose

Filtering: In-line particle filters and optional activated charcoal filter.

Slde Pack case: Molded high impact plastic case with carrying handle and shoulder strap

Eiectrlcal protection: Refer to Section 5 Standard accessories:

Variable (see Figure 1-2)

1) Instrument carrying and storage Case 2) Fuel filling hose assembly 3) A.C. battery charger 4) Earphone 5) Various pickup fixtures

1) Gas chromatograph option 2) Portable strip chart recorder 3) Activated charcoal filter; also used

4) Dilution valve 5) Septum adapter for use with gas

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with desiccant as a moisture trap

chromatograph option

SECTiON 2 DETAILED OPERATING PROCEDURES 2.1 GENERAL

m e procedures in this section are broken into five parts: (1) Starting, (2) Operating, (3) Shut Down, (4) Fuel Refilling, and (5) Battery Charging. After familiarization

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, the summarized procedures 3 may be used for simplicity. optional applications for the in-

- strument, - the- comprehensive - detailed procedures- described in this section may seem complex. However, In normal applications the operating procedures are quite simple. A condensed operating procedure check list is provided inside the cover of the Side Pack Assembly. Refer to Section 7 for operating procedures relative to major optional accessories such as the Gas Chromatograph Option.

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2.2 SYSTEM CONTROLS, INDICATORS AND CON- NECTORS

Tables 2-1 and 2-2 describe the functions of the various controls, indicators and connectors illustrated in Figure 1-1. Unless otherwise noted, the listings in Tables 2-1 and 2-2 are applicable to both the Model OVA- 11 8 and OVA-1 28.

TABLE 2-1 SIDE PACK ASSEMBLY

Controlsllndicators - Functlon lNSTRlBA7T Test Switch - This 3 position toggle switch turns on all instrument electrical power except the pump and alarm power and also permits display of the'battery charge condition on the readout meter. PUMP (ON-OFF) Switch - This toggle switch turns on power to the internal pump and audio alarms. Igniter Switch - This momentary push button switch connects power to the igniter coil in the detector chamber and simultaneously disconnects power to pump. CALIBRATE Switch (range selector) - This 3 position toggle switch selects the desired range: X1 (0-10 ppm); X10 (4100 ppm); XlOO (0- 1 .OOo ppm). CALIBRATE ADJUST (zero) Knob - This potentiometer is used to "zero" the instrument. GAS SELECT Knob (span control) - This ten- turn dial readout potentiometer sets the gain of the instrument commonly reierred to as span ccn:rol. Recorder Connector - This 126 series Spin Am- phenol connector is used to connect the instrument to an external monitor with the following pin connections.

Pin E - plus 12VDC Pin H -Ground Pin A - Signal 0-SVDC (OVA-118 only) Pin B - Signal MVDC (OVA-128 only)

Recharger Connector - This BNC connector is used to connect the battery pack to the battery recharger assembly. H 2 TANK VALVE - This valve is used to supply or close off the fuel supply from the hydrogen tank.

H 2 TANK PRESSURE Indicator - h i s hi@l '

pressure gauge measures the pressure in the hydrogen fuel tank - which is an indication of fuel

~2 SUPPLY VALVE - This valve is used to supp ly or close off the hydrogen fuel to the detector chamber. H 2 SUPPLY PRESSURE Indicator - This low pressure gauge is used to monitor the hydrogen pressure at the capillary restrictor. SAMPLE FLOW RATE Indicator - This indicator is used to monitor the sample flow rate. Refill Connection - This 114" AN fitting is used to connect the hydrogen refill hose to the instrument. REFILL VALVE - This valve is used to open one end of the instrument fuel tank for refilling with hydrogen. Earphone Jack - This jack is used to connect the earphone; it turns off speaker when used. VOLUME Knob - This potentiometer adjusts the volume of the internal speaker and earphone. Readout and Sample Connectors - These cor+ nectors are used to connect the sample hose and umbilical cord from the ProbelReadout Assembly to the Side Pack Assembly.

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TABLE 2-2 PROBElREAOOUT ASSEMBLY

Controlsllndicators - Functlon A) Meter - This 2500 linear scaled meter displays

the output signal level in ppm. 8) Alarm Level Adjust Knob - This potentiometer

(located on the back of the Readout Assembly) is used to set the concentration level at which the audible alarm is actuated.

I 2.3 STARTlNG PROCEDURE 2.3.1 INITIAL PREPARATION FOR USE 2.3.1.1 INITIAL ASSEMBLY (Reference Figure 1-2)

(1) Connect the adjustabl&dWjt?rprobe to the Readout assembly with-the captive locking nu:. Ensuie tfiz: the probe is seated fi:;nly in the Readout Assembly.

( 2 ) Select the cesir-25 pickup fixture and c.ieck that a particle filter is installed.

(3) Connect the pickup fixture to the probe US- ing the knurled locking nut.

(4) Connect the umbilical cord and sample hose to the Side Pack Assembly.

(1) Check to ensure that a particle filter is installed in the close area sampler.

(2) Connect the close area sampler directly to the Readout Assembly.

(3) Connect the umbilical cord and sample hose to the Side Pack Assembly.

a) Nonnal Survey Configuration : 8

b) " a w e Area" Survey Configuration

2.3.1.2 SERVlClNG a) fueling: Pure. dry hydrogen can normally be

f'; 3959 INTRODUCTlON

The Century Model OVA-128 Portable Organic Vapor ; I I

Analyzer (OVA) is a highly sensitive instrument desian- ed to measure trace quantities of organic materialsin air. It is essentially a hydrogen flame ionization detector such as utilized in laboratory gas chromatographs and has similar analytical capabilities. The flame ionization detector is an almost universal detector for organic compounds with the sensitivity to analyze for them in the parts per million range (V IV) in air in the presence of moisture, nitrogen oxides, carbon monoxide and carbon dioxide.

The instrument has broad application, since i t has a continuous, chemically resistant air sampling system and can be readily calibrated to measure atmost all organic vapors. It has a single linearly scaled readout from 0 ppm to 10 ppm with a X1. X10, XlOO range switch. Designed for use as a portable survey instrument. it can also be readily adapted to fixed remote monitoring or mobile installations. It is ideal for the determination of many organic air pollutants and in the monitoring of air in potentially contaminated areas.

The OVA-128 is certified intrinsically safe by Factory Mutual Research Corporation (FM) for use in Class I, Division 1, Groups A, 8. C & 0 hazardous environments.

SIDE PACK ASSEMBLY

Simihr foreion certifications have cluding EAsiiEFA and Cerchar appmval for Group IC. Temperature Class T4 and equivalent approval from the Japanese Ministry of Labor. This requirement is especially significant in industries where volatile flammable petroleum or chemical products are manufac- tured, processed or used and for instruments which are actually used in portable ,surveying and in analyzing concentrations of gases and vapors. Such instruments must be incapable, under normal or abnormal conditions. of causing ignition of the hazardous atmospheric mixtures. In order to maintain the certified safety. i t is important that the precautions outlined in this manual be practiced and that no modlflcation be made to these instruments.

Sections 1 through 6 herein apply to the basic instrument. Section 7 contains information relative to options which are available and which may or may not have been purchased with your OVA.

It is highly recommended that the entire manual be read before operating the instrument. It Is essential that all portions relating to safety of operation and maintenance, including Section 5. be thoroughly understood.

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FIGURE 1-1 ~ PORTABLE ORGANIC VAPOR ANALYZER Model OVA-1 28

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purLhased locally or in a high grade from the Matheson Company. of _East .Rutherford, New Jersey. The maximum instrument supply bottle pressure is 2300 PSIG. A high pressure hydrogen filling hose assembly Is provided with the instrument. This assembly includes the proper fittings for the instrument and supply bottle, and a three-way filllbleed valve. Initial fueling and subsequent refilling, using the Cen- tury high pressure filling hose, should be accomplished in accordance with the detailed instructions described in Section 2.6 of this manual. Battery Check: Move INSTRlBAlT Test Switch to the BAlT position and ensure battery is charged by reading the indication on the readout meter. Callbratlon: Standard factory calibration is per- formed using methane in air. The GAS SELECT (span) Control is set and locked to the position for calibration to methane (factory setting is 300). If the instrument is calibrated for other clrt2nic vacors. !h? reading on the GAS - - . . - --- -_-. .^J - - - - _ - - . :-- ..-," =-^ . , t L I

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SAFETY PRECAUTIONS Certain safety precautions must be followed in using

the instrument. Hydrogen gas, when mixed with air, is highly flammable. Operating and refueling instructions should be strictly followed to ensure safe, reliable operation. Section 5 of the manual provides detailed safety precautions.

2.3.2 TURN ON PROCEDURE The GAS SELECT control should be preset to the

desired dial indication prior to turn on. The procedure for determining this setting is contained in Section 4 of this manual. The instrument, as received from the factory, is set ta measure in terms of methane in air.

Move the INSTR Switch to ON and allow five minotesfor warm up. To set the audible alarm to a predetermined level. first turn the PUMP Switch to ON, then adjust the meter pointer to the desired alarm level, using the CALIBRATE ADJUST (zero) Knob. Turn the Alarm Level Adjust Knob on the back of the Readout Assembly until the audible alarm just comes on. Adjust speaker volume with VOLUME Knob. If earphone is used, plug in and readjust the volume as desired. The instrument is then preset to activate the alarm when the level exceeds that of the setting. Move the CALIBRATE Switch to XlO and adjust the meter reading to zero with the CALIBRATE ADJUST (zero) Knob. Ensure the PUMP Switch is ON and observe the SAMPLE FLOW RATE Indicator. Indication should be approximately 2 units. Open H2 TANK VALVE one (1) turn and observe the reading on the H2 TANK PRESSURE In- dicator. (Approximately 150 psi of pressure is

needed for each hour of operation.) Open H2-SUPPLY VALVE-112 to 1-turn and - - -

observe the reading on the H2 SUPPLY PRESSURE Indicator.

CAUTION Do not leave H2 SUPPLY VALVE open when the pump is not running. as this will allow hydrogen to accumulate in the detector chamber.

Confirm that meter is still reading zero (readjust if required). Depress igniter button. There will be a slight "pop" as the hydrogen ignites and the meter pointer will move upscale of zero. Immediately after ignition, release the igniter button. Do not depress igniter button for more than 6 seconds. If burner does not ignite, let instrument run for several minutes and try again. After ignition, the meter pointer will indicate the background concentration. This background level is nulled c1.; - 5 t - g the C>Li39~. iE 43,USTfzero) Kzcc>. - - - - - _ _ - - _ _ _ -

NOTE Since the OVA utilizes the sample air drawn by the pump into the detector chamber as the only source of air to support the hydrogen flame, without adjustment the instrument will read the actual background concentration (ppm) of all hydrocarbons present at a given location.

Move instrument to an area which is representative of the "lowest ambient background concentration" (cleanest air) to be surveyed. Move the CALIBRATE Switch to X1 and adjust the meter to read 1 ppm with the CALIBRATE AD- JUST (zero) Knob.

NOTE Adjustment to 1 ppm (rather than 0) is necessary in the X1 range because of the sensitivity of the OVA. This permits minor downward fluctuations in the normal background level without dropping below 0, which would actuate the flameout alarm. It is important, therefore, to remember during the subsequent survey that 1 ppm must be subtracted from all readings. Therefore, a 1.8 ppm reading would actually be only 0.8 PPm.

If the alarm level is to be set above the normal background detection level, turn the Alarm Level Adjust Knob on the back of the Readout Assembly until it actuates slightly above background . THE INSTRUMENT IS NOW READY FOR USE.

OPERATING PROCEDURES Set the CALIBRATE Switch to the desired

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. ' r; ; -,: , 3959 range. Using one hand operatlon. survey the areas of interest while observing the meter andlor listening for the audible alarm indication. For ease of operation, carry the Side Pack Assembly positioned on the side opposite the hand which holds the ProbelReadout- Assembly. For broad surveys outdoors, the pickup fixture should be positioned several feet above ground level. When making quantitative reading or pinpointing. the pickup fixture should be positioned at the point of interest.

b) When organic vapors are detected, the meter pointer wil l move upscale and the audible alarm will sound when the preset point is exceeded.

- The frequency of the audible alarm will increase as the detection level increases.

c) If the f l a m w t alarm is actuated, ensure that the pump is running, then press the igniter button. Under normal conditions, flameout results from sampling a gas mixture that is above the lower explosive level which causes the H2 flame to extinguish. If this is the case, reignC tion is all that is required. Another ;?soiSI=. c ~ u s e :cr 'Zme-cct .x: :'e be restriction of the sample flod line which .:ould not allow sufficient air into the chamber to support combustion of the H2 flame. The normal cause for such restriction would be a clogged particle filter or other restriction in the line. It should be noted that the chamber exhaust port is on the bottom of the case and blocking this port with the hand will cause fluctuations andlor flame-out.

2.5 SHUT DOWN PROCEDURE

down of the instrument The following procedure should be followed for shut

Close H2 SUPPLY VALVE. Close H2 TANK VALVE. Move INSTR Switch to OFF. Wait5 seconds and move PUMP Switch to OFF. INSTRUMENT IS NOW IN A SHUT DOWN COW FIGURATION. . FUEL REFILLING The instrument should be completely shut down as described in Section 2.5 herein during hydrogen tank refilling operations. The refilling should be done in a ventilated area. There should be no potentlal Igniters or flame In the area. If you are making the first filling of the instrument or i f the filling hose has been allowed to fill with air, the filling hose should be purged with N2 or H2 prior to filling the instrument tank. This purging is not required for subsequent fill- ings. The filling hose assembly should be left attached to the hydrogen supply tank when possible. Ensure that me FlLLlBLEED Valve on me instrument end of the hose is In the OFF position.

Connect the hose to the refill connection on the Side Pack Assembly.

d) Open the hydrogen supply bottle valve slightly. Open the REFILL VALVE and the H 2 TANK VALVE on the instrument panel and place the flLLlBLEED Valve on the filling hose assembly in the FILL position. The pressure in the instrument tank will now be indicated on the H 2 TANK PRESSURE Indicator.

e} After the instrument fuel tank is filled, shut off the REFILL VALVE on the panel, the FlLLlBLEED Valve on the filling hose assembly and the hydrogen supply bottle valve. The hydrogen trapped in the hose should now be bled off to atmospheric pressure. CAUTION should be used in this operation as described in Step (g) below, since the hose will contain a Significant amount of hydrogen at high pressure.

g) The hose is bled by turning the FILLIBLEED Valve on the filling hose assembly to the BLEED position. After the hose is bled down to atmospheric pressure, the FlLLlBLEED Valve shculd 59 turn%d !o !he FlLL zosition to allow the hydrogen trapped in the connection fittings to go into the hose assembly. Then. again, turn the FlLLlBLEED Vaive to the BLEED position and exhaust the trapped hydrogen. Then turn the FlLLlBLEED Valve to OFF to keep the hydrogen at one atmosphere in the hose so that at the time of the next filling there will be no air trapped in the filling line.

h) Close the H2 TANK VALVE. i) With the H2 TANK VALVE and the H2 SUPPLY

VALVE closed, a small amount of H2 at high pressure will be present in the regulators and plumbing. As a leak check, observe the H2 TANK PRESSURE Indicator while the re- mainder of the system is shut down and ensure that the pressure indication does not go down rapidly, indicating a significant leak. If it does decrease rapidly (greater than 350 PSlGIhr.). there is a significant leak in the H2 supply system.

f)

2.7 BAlTERY RECHARGING a) Plug charger BNC connector into mating con-

nector on battery cover and insert AC plug into 115 VAC wall outlet. Never charge in a hazardous area or environment.

b) Move the battery charger switch to the ON position. The light above the switch button should illuminate. Battery charge condition is indicated by the meter on the front panel of the charger; meter will deflect to the right when charging. When fully charged, the pointer will be in line with "charged" marker above the scale.

d) Approximately one hour of charging time is re- qirired for each hour of operation. However, an overnight charge is recommended. "The charger can be left on indefinitely without

c)

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a!!m!B@t " damaging the batteries. When finished, move the battery charger switch to OFF and discon-

m e fdlowlng are 8pecl.l Instructlon8 relatlve to bat- ted- which have been allowed to completely dlsdwge.

It has been established that the above battery recharging procedures may not be sufficient when the operator of the instrument has inadvertently left the IN- STR Switch ON for a period of time without recharging and allowed the battery to complotely discharge.

When this happens and the above procedures fail to recharge the battery, the following should be ac- ComDlished:

- nect-from the Side-Pack-Assembly.- - - -

Remove the battery from the instrument case. Connect to any variable DC power supply. Apply 40 volts at 112 amp maximum. Observe the meter on the power supply fre- quently and as soon as the battery begins to draw current, reduce the voltage on the power supply at a slow rate until the meter reads approximately 15 volts. NOTE: The time required to reach the 15 volt reading will depend on degree of discnarge. PPoezt steps a), b), c ) . and d) above to continue charging.

DC CHARGER The optional DC charger is designed to both charge the battery and to provide power for operating the instrument from a 12 volt DC source, such as vehicle power. Connect the DC charger cord to the connector on the battery cover of the Side Pack Assembly. Plug the line cord into the vehicle cigarette lighter or other power source connection. In mobile applications, the DC charger is used to supply vehicle power to the instrument. Therefore, it may be left connected at all times. CHARCOAL FILTERING

When it is desired to preferentially remove the heavier hydrocarbons, such as those associated with automobile exhaust, gasoline, etc.. simply remove the pickup fixture from the end of the probe and install the optional charcoal filter assembly.

This same charcoal filter assembly can be installed directly into the Readout Assembly by using the adapter provided.

2.9 MOISTURE FILTERING Filtering of moisture in the sample is not normally r e

quired. However, when moving in and out of buildings in cold weather, excessive condensation can form in the lines and detector chamber. In this case, the charcoal filter adapter can be filled with a desiccant such as "Drierite" which will filter out the moisture contained in the sample.

SECTION 3 SUMMAFUZED owunffi PROCEDURES 3.1 GENERAL

The Procedures presented in this section are intended for use by personnel generally familiar with the operation of the instrument. Section 2 presents the comprehensive detailed operating procedures.

39:59 ' ,

it is assumed that, prior to start up the positions of all switches and valves are in shut down configuratlon as describedinparagraph 3.3. - . - . - - - . - -

START UP Move PUMP Switch to ON and check battery condition by moving me INSTR Switch to the BAlT posltion. Move INSTR Switch to ON and allow five (5) minutes for warm-up. Set Alarm Level Adjust Knob on back of Readout Assembly to desired level. Set CALIBRATE Switch to X10 position, use CALIBRATE Knob and set meter to read 0. Move PUMP Switch to ON position then place instrument panel in vertical position and check SAMPLE FLOW RATE indication. Open the H2 TANK VALVE and the H2 SUPPLY VALVE. Depress Igniter Button until burner lights. Do not depress Igniter Button for more than SIX (6) seconds. (If burner does not ignite. let instw ment run for several minutes and again attempt ignition.) Use CALISRATE Knob to "zero" cut ambient

ppm,-set CALJBRATE Switch to X1 and readjust zero on meter. To avoid false flameout alarm indication. set meter to 1 ppm with CALIBRATE Knob and make differential readings from there.

k - ~ b - - r . - - < . _ _ C . Fc: - 3 ~ i r r r . o capfi+":lf-: bslT*,v 10

SHUT DOWN Close the H2 SUPPLY VALVE and the H2 TANK VALVE. Move the INSTR Switch and PUMP Switch to OFF. Instrument is now in shut down configuration.

SECTION 4 CALIBRATION 4.1 GENERAL

The OVA is capable of responding to nearly all organic compounds. For precise analyses it will be necessary to calibrate the instrument with the specific compound of interest. This is especially true for materials contalning elements other than carbon and hydrogen.

The instrument is factory calibrated to a methane in air standard. However, it can be easily and rapidly calibrated to a variety of organic compounds. A GAS SELECT control is incorporated on the instrument panel which is used to set the electronic gain to a particular organic compound.

Internal electronic adjustments are provided to calibrate and align the electronic circuits. There are four (4) such adjustments all located on the electronics board. One adjustment potentiometer, R-38. is used to set the power supply voltage and is a onetime factory adjustment. The remaining three adjustments. R-31, R- 32 and R-33 are used for setting the electronic amplifier gain for each of the three (3) calibrate ranges. Access to the adjustments is accomplished by removing the instrument from its case. Figure 4-1 indicates the location of me adjustments.

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4.2 ELECTRONIC ADJUSTMENTS

at the factory using methane in air sample gases. Primary calibration of this instrument is accomplished

GAIN ADJUSTMENT Place instrument in normal operation with CALIBRATE Switch set to X10 and GAS SELECT control set to 300. Use the CALIBRATE ADJUST (zero) Knob and adjust the meter reading to zero. Introduce a methane sample of a known concentration (near 100 ppm) and adjust trimpot R 32 on circuit board (see Figure 4-1 for location) so that meter reads equivalent to me known sample. This sets the instrument gain for methane with the panel mounted gain adjustment (GAS SELECT) set at a reference number of 300. Turn off H2 SUPPLY VALVE to put out flame.

BIAS ADJUSTMENT Leave CAL18RATE Switch on X10 position and use CALIBRATE ADJUST (zero) Knob to adjust meter reading to 4 ppm. Place CALIBRATE Swiich in X1 position and, using trimpot R-3l on circuit board. adjust meter reading to 4 ppm. (See Figure 41) Move CALIBRATE Switch to X10 position again. Use CALIBRATE ADJUST (zero) Knob to adjust meter to a reading of 40 ppm. Move CALIBRATE Switch to XI00 position and use trimpot R-33 on circuit board to adjust meter reading to 40 ppm. Move CALIBRATE Switch to X10 position and use CALIBRATE ADJUST (zero) Knob to adjust meter reading to zero. Unit is now balanced from range to range, calibrated to methane, and ready to be placed in normal service.

FIGURE 4-1. LOCATION OF ELECTRONIC ADJUSTMENTS

4.3 CALIBRATION TO OTHER ORGANlC VAPORS 4.3.1 S m N G GAS SELECT CONTROL (Span)

Prlmary calibration of the instrument is accomplished using a known mixture of a specific organic vapor compound. After the instrument is in operation and the "normal background" is "zeroed out", draw a sample of the calibration gas into the instrument. The GAS SELECT Knob on the panel is then used to shift the readout meter indication to correspond to the concentration of the calibration gas mixture.

The instrument is then calibrated for the vapor mixture being used. After this adjustment, the setting on the "digidW" is read and recorded for that partlCUhr organic vapor compound. This exercise can be perform- ed for a large variety of compounds and when desiring to read a particular compound the GAS SELECT control is turned to the predetermined setting for the compound. Calibration on any one range automatically calibrates the other two ranges.

4.3.2 USING EMPIRICAL DATA Relative response data may be obtained, which can

then be used to estimate concentrations of various vapors. With the instrument calibrated to methane, obtain the concentration reading for a calibration sample of the test vapor. The relative response, in percent, for that test vapor would then be the concentration readlconcentration of the calibrated sample X 100.

4.3.3 PREPARATION OF CALIBRATION STANDARDS 4.3.3.1 COMMERCIAL SAMPLES

Commercially available standard samples offer the most convenient and reliable calibration standards and are recommended for the most precise analyses. Always remember to obtain the cylinder with the desired sample and the "balance as air". Sample should be drawn from the cylinder into a collapsed sample bag, then drawn from the bag by the instrument to prevent a pressure or vacuum at the sample inlet.

4.3.3.2 PURE GASEOUS SAMPLES Obtain a large collapsible sample bag, preferably

polyethylene such as a 40 gallon trash can liner. Insert a tube into the bag opening and tie shut around the tube. The tubing should have a shut-off valve or plug and be suitable for connecting the OVA input tube. Determine the volume of the bag by appropriate means (i.e.. wet- test meter, dimensions of the bag, etc.). Forty gallon polyethylene bags provide a volume of approximately 140-160 liters. For gas samples, flush a 10 cc hypodermic syringe with the compound to be tested and then inject a 10 cc sample through the wall of the air-filled bag. Im- mediately after withdrawing the needle, cover the hole with a piece of plastic tape. Allow a few minutes for the sample to completely diffuse throughout the bag. Agita- tion will ensure complete diffusion. Connect the outlet tube to the OVA and take a reading. To verify repeatability of sampling technique, disconnect the bag and inject a second sample of the gas into the bag without emptying. Since only 2 or 3 liters wil l have been removed, the overall volume change will be small and the instrument reading should now be twice that of the

(Model OVA-118 shown; location typlcal to OVA-128) w ,.. r m

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original. The concentration in ppm (VIV) will be equal to the sample size in cc divided by the volume of the bag in liters times 1OOO; For example, a 10 cc gas sample when- placed in a 160 liter bag wlll provide a sample of 63 ppm, Le.. 10 X 10401160 equals 63 ppm.

4.3.3.3 GASEOUS AND LIQUID SAMPLES (Alternate

Obtain a five (5) gallon glass bottle and determine its volume by measuring the volume of water needed to f i l l it (use of a lo00 ml graduated cylinder, obtainable from ‘scientific supply houses, is convenient). Another approach is to weigh the empty bottle, fill it with water and weigh again. The difference between the two values is the weight of water. By multiplying the weight of water in pounds by 0.455, you obtain the volume of the bottle in liters. Empty the water out and allow the bottle to dry. Place a one-foot piece of plastic tubing in the flask to aid in mixing the vapors uniformly with the air. The volume of such a bottle should be about 20 liters, which Is 20,ooO ml. If the volume were 20,OOO ml, then a 2 ml sample of a gas placed In the bottle would be equivalent to 200 ml per 2 million mi or 100 ppm (VIV). Use of a gas tight syringe. readzi2le in 0.Sl nl. allcws the preparation of mixtures in the 1 - 2 ppm range. which are sufficient for the quantitative astirnA;ion oi ::~z?z~:::~~::. ..:. ?:t‘5’0‘ stopper is loosely fitted to the top of the bottle and the needle of the syringe placed inside the jug neck and the stopper squeezed against the needle to decrease leakage during sample introduction. Inject the sample into the bottle and withdraw the needle without removing the stopper. Put the stopper in tight and shake the bottle for a few minutes with sufficient vigor that the plastic tubing in the bottle moves around to ensure good mixture of the vapors with the air.

For liquid samples, use of the following equation will allow the calculation of the number of microliters of organic liquid needed to be placed into the bottle to make 100 ppm (VIV) of vapor.

V1 equals V2 X Mwf 2440

Method)

W - Volume of liquid in mlcroilters needed to make an air mixture of 100 ppm (VIV)

V2 - Volume of bottle in liters Mw - Molecular weight of substance D - Density of substance

This procedure has the advantage that you can see when all of the organic liquid has vaporized and the volume can be determined readily.

For liquid samples, an alternate procedure involves the use of a diffusion dilution device such as that described by Oesty. Geach and Goldup in “Gas Chromatography”. R.P.W. Scott, ed., Academic Press, New York, 1961.

4.4 THEORY Theoretical background and empirical data related to

the Century Organic Vapor Analyzer is presented in 4.4.1 and 4.4.2.

4.4.1 HYDROCARBONS 3959 , ’ In general. a hydrogen flame ionization detector is

more sensitive for hydrocarbons than any other class of organic compounds. The response of the OVA varies from compound to compound, but gives excellent repeatable results with all types of hydrocarbons; i.e.. saturated hydrocarbons (alkanes), unsaturated hydrocarbons (alkenes and alkynes) and aromatic hydrocarbons.

The typical relative response of various hydrocarbons to methane is as follows:

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Compound Methane Propane N-butane N-pentane Ethylene Acetylene Benzene Toluene Ethane

Relatlve Response (percent) 100 (reference) 64 61

100 85

200 150 120 90

4.4.2 OTHEF( ORGANIC COMPOUNDS Compouncs coniaicins oxy;an, scth as alcchols.

others. :1???4e5. r z r b d i c acid and esters give a somewhat ‘lower response [n;a iai,G; G C I S L T ; ~ ~ i:: hydrocarbons. This is particularly noticeable with those compounds having a high ratio of oxygen to carbon such as found in the lower members of each Sen- which have only one, two or three carbons. With com pounds containing higher numbers of carbons, the e t fect of the oxygen is diminished to such an extent that the response is similar to that of the corresponding hydrocarbons.

Nitrogen-containing compounds (i.e., amines, amides and nitriles) respond in a manner similar to that observed for oxygenated materials. Halogenated corn pounds also show a lower relative response as corn pared with hydrocarbons. Materials containing no hydrogen, such as carbon tetrachloride, give the lowest response; the presence of hydrogen in the compounds results in higher relathe responses. Thus, CXCI:, gives a much higher response than does CCk. As in the other cases, when the carbon to halogen ratio is 5 1 or greater, the response will be similar to that observed for simple hydrocarbons.

The typical relative response of various COInpoundS to methane is as follows:

Methane 100 (calibration sample)

60 Acetone Methyl ethyl ketone 80 Methyl isobutyl ketone 100

Ketones

Alcohols Methyl alcohol 15

65 Ethyl 25 l-ProPYl

9

” Halogen compounds a ,

Carbon tetrachloride 10 Chloroform 65 Trichloroethylene . TO Vinyl chloride 35

The OVA has negligible response to carbon monoxide and carbon dioxide which evidently, due to their struc- ture, do not product appreciable ions in the detector fkme. Thus, other organic materials may be analyzed in me presence of CO and COZ.

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3959 0’

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SECTION 5 S A F W CONSIDERATtONS 5.1 GENERAL

The Models OVA-108. OVA-120 and OVA-138 have been tested and certified by Factory Mutual Research Corporation (FM) as intrinsically safe for use in Class I, Division 1, Groups A. 8. C 8 D hazardous atmospheres. Similar foreign certifications have been obtained, including BASEEFA and Cerchar approval for Group IIC,. Temperature Class T4 on the Models OVA-lW,OVA-128 and OVA-138. and equivalent approval from the Japanese Ministry of Labor for the Model OVA-128. Special restrictions must be strictly adhered to, to ensure the certification is not invalidated by actions of operating or service personnel.

Al l flame ionization hydrocarbon detectors are potentially hazardous since they burn hydrogen (H2) or H2 mixtures in the detector cell. Mixtures of H2 and air are flammable over a wide range of concentrations whether an inert gas such as nitrogen (N2) is present or not. Therefore. the recommended precautions and p r e cedures zk=uld be !c,!Z..vad for mzxi,Turn ssfety. Safety considerz:.cr.s was a d~-+x kc::: :a .;> les4G-n c : :?-3

Organic VsTor Apalyzer [OVA). All connectors are of the permanent type as opposed

to quick disconnect. To protect against external ignition of flammable gas mixtures, the flame detection chamber has porous metal flame arrestors on the sample input and the exhaust ports as well as on the H2 inlet connector. The standard battery pack and other circuits are internally current limited to an intrinsically safe level.

5.2 OPERATING. SERVICING AND MODIFYING It is imperative that operation and service procedures

described in this manual be carefully followed in order to maintain the intrinsic safety which is built into the OVA. No modiflca~on to the Instrument Is permissible. Therefore, component replacement must be accomplished with the same type parts.

5.3 ELECTRICAL PROTECTION The 12V battery power supply circuit is current limited

to an intrinsically safe level. Fuses are not utilized and ail current limiting resistors and other components which are critical to the safety certification are en- capsulated to prevent inadvertent replacement with components of the wrong value or specification. Under no circumstances should the encapsulation be removed.

5.5 H2 FLOW RESTRICTORS Hydrogen gas gains heat when expanding and,

therefore, should not be rapidly released from a high--- pressure tank to a low pressure environment. Flow restricton are incorporated in the H2 refill fitting and H2 is resMcted on the output side of the tank by the low How rate control system. In additlon. a special flow restrictor is incorporated In the FlLLlBLEED valve of the hydrogen filling hose assembly. These precautions limit the Row rate of the H2 to prevent ignition due to self-heat from expansion.

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5.6 DETECTOR CHAMBER The OVA has a small flame ionization chamber cavity

with sintered metal ftarne arrestors on both the input and output ports. The chamber is ruggedly constructed of teflon such that even if highly explosive mixtures of H2 and air are inadvertently created in the chamber and ignited, the chamber would NOT rupture.

5.7 H2 FILLING AND EMPTYING OPERATIONS Precautions should be taken during H2 filling or H2

tank emptying operations to ensure that there are no sources of ignition in :he irnne&a:a 2 e a . Since :he instrument at 22C.3 i S I G h ~ ~ c ' s c n ! y 5 , ; :u. f:. zf Y2, :hs iO:tl cuan::ty, i f :?'eased :o :he atr;=?s?nero. dculd be quickly diluted to a non-flammable level. There is. however, the possibility of generating flammable mixtures in the immediate vicinity of the instrument during the filling or emptying operations i f normal care is not exercised.

5.8 VENTING The OVA case is vented to eliminate the possibility of

trapping an explosive mixture of H2 and air inside the case.

5.4 FUEL SUPPLY a TANK The OVA fuel tank has a volume of 75 to 85 cc which,

when filled to the maximum rated pressure of z)oo PSIG. holds approximately 5/8 cubic foot of gas. The fuel used in the OVA is pure hydrogen which can be readily purchased in a highly pure form at nominal cost. The H2 tanks used in the instrument are made from stainless steel. proof-tested to 6,000 PSIG and 100% production tested to 4.000 PSIG.

3959 SECTION 6

MAINTENANCE 6.1 GENERAL

This section descrlbes the routine maintenance schedule recommended and provides procedures for trouble shooting malfunctions or failures in the instrument.

Appendix "A" to this manual contains the assembly drawings and associated parts list for the Slde Pack Assembly and two major subassemblies; the Electronic Component Assembly and the Cylinder Assembly. These drawings and parts lists may be used for locating and identifying components. Also included in Appendix "A" Is a schematic wiring diagram showing intercon- necting wiring between major electronic assemblies and typical signal levels at selected points on the certified instruments. The enclosed drawings and parts lists are subject to change without notice and part replacement on any certified instrument should be verified to comply with the "no modifications permitted" requirement.

IC:, u TI c N , I - _ - _- - 1 -,-.ir,:srs :? ;- _ _ ':i ;,-L-,- :?

ing maintenance. It is essential that all portions of this manual relating to safety of operation, servicing and maintenance, including Section 5. be thoroughly understood. There should be no poten-

iarniriar :'#ILI Inst;L;T-,snt ;;zra;icn DSiCid 4SriOfii-i-

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- - - tial igniters or flame in the area when filling, empty- Ing or purging the hydrogen system and the In- ment should be turned off. Extreme care should be exercised to ensure t h t required parts re@acement is accompllshed with the same parts specifled by Century. This Is especially necessary on the Models OVA-108, OVA- 128 and OVA-138 In order that their certlflcatlon for use In hazardous atmospheres be maintained. No modlficatlons are permitted. Dlsassemble In- ment only In a Mm-hetardous atmosphere.

6.2 ROUTINE MAINTENANCE

handling system. Note that Rgure 6 1 is a flow diagram of the basic gas

6.2.1 flLlERS 6.2.1.1 PRIMARY FILTER

This filter is located behind the sample Inlet connector (Fittlng Assembly) on the Side Pack Assembly and is removed for cleaning by using a thin wall socket to unscrew the Fitting Assembly. The filter cup, "0" ring and loading spring will then come out as shown in the Side Pack Assembly drawing in Appendix "A". ?:a

ing out or washing in a solvent. If a solvent is used, care should be taken to ensure that ail solvent is removed by blowing out or heating the filter. Reassemble in reverse order ensuring that the "0" ring seal on the Fitting Assembly is intact.

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FIGURE 6-1. Flow Diagram - Gas Handling System 21

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6.2.1.2 PARTICLE-FILTERS A particle filter is lo&ted-in-each-pickup fixture. -One-

of these filters must be In the sample line whenever the instrument is in use. The Models O V A 4 and OVA-138 use a disposable cellulose filter which should be changed as often as required. The Models OVA-98, OVA-108, OVA-118 and OVA-128 use a porous metal filter which can be replaced or cleaned using the cleaning procedure in paragraph 6.2.1.1.

6.2.1.3 MIXERIBURNER ASSEMBLY FILTER Another porous metal particle filter is incorporated in

the MixerlBumer Assembly which screws into the Preamp Assembly. See Side Pack Assembty drawing. This-filter is used as the sample mixer and inlet flame arrestor in the chamber. This filter should not become contaminated under normal conditions but can be cleaned or the assembly replaced if necessary.

Access to this filter for output surface cleaning is gained by simply unscrewing the exhaust port from the Preamp Assembly without removing the instrument from the case. The OVA-108, OVA-128 and OVA-138 instruments require removal of the safety cover prior to unscrewing the exhaust port. The Filter Assembly can now be seen on the side of the chamber (Preamp Assembly) and can be scrapped or cleaned with a small wire brush.

If filter replacement is required, install a new or factory rebuilt Mixer/Burner Assembly. In several OVA models, this requires removal of the Preamp Assembly.

6.2.1.4 EXHAUST FLAME ARRESTOR A porous metal flame arrestor is located in the ex-

haust port of the detector chamber (Preamp Assembly). See Side Pack Assembly drawing. It acts as a particle filter on the chamber output and restricts foreign matter from entering the chamber. This filter may be cleaned, i f required, by removing the exhaust port from the Preamp Assembly. The exhaust port is removed from the bottom of the case without case removal. Note that the filter is captive to the exhaust port on the Models OVA-108, OVA-128 and OVA-138. Clean the filter with a solvent or detergent but ensure that it is dry and any solvent completely baked out at 12OOF before reinstall- ing.

6.2.2 PICKUP FIXTURES The pickup fixtures should be periodically cleaned

with an air hose and/or detergent water to eliminate foreign particle matter. If a solvent is used, the fixture should be subsequently cleaned with detergent and baked out at 120°F to eliminate any residual hydrocarbons from the solvent.

6.2.3 SEAL MAINTENANCE - CYLINDER ASSEMBLY 6.2.3.1

After some time, the teflon washers under each valve packing nut can "cold flow" (move with pressure) and allow hydrogen to leak. Leakage can be determined by using Leak-Tec, Snoop or a soap solution around the valve stems. This leakage can usually be stopped by tightening the compression nut (adapter) as outlined

t i2 TANK, H2 SUPPLY AND REFILL VALVES

below. See Side Pack Assembly and Cyllnder Assembly . . - - - . .. .. .. . . . . .. . . . - - -. _ _ - .

Remove instrument from the case by unlocking the four (4) 114 turn fasteners on the panel and removing the exhaust safety cover (if included), exhaust port and refill cap nut. Be sure refill valve is closed before removing refill cap nut. Remove the valve knob screw and knob. Loosen the panel nut with a 314" wrench. m e valve compression nut is located just under the panel. Tighten the compression nut- usually not more than 114 turn.

This compression is against soft material and only i small amount of force is necessary to sufficiently compress the teflon washers. If, after tightening leakage still occurs, it would be advisable tc replace the two teflon washers, as follows:

Drain hydrogen system slowly and to the exten* necessary to work on the leaking valve(s) Observe safety precautions (See Section 5) There should be no potential igniters in the area. Disconnect the capillary tube from the manifolc at low pressure gauge (ti2 Supply Pressure). Remove ail three (3) knob screws and knobs. Remove the three (3) panel nuts and washers. Carefully remove the tank assembly from thr panel. NOTE: If OVA has GC Option installed the GC valve assembly must be loosened o removed in order to remove the tank assemblt from the panel. Remove the compression nut on the valve ths is not sealing properly. Remove the stem b unscrewing it from the valve body. Observe tht sandwich of metal and teflon washers and not1 their order. Visually check the Kel-F seat on the stem fo cracks or foreign material. Wipe clean, I

necessary, with a lint free cloth (no solvents c oils) and replace if damaged. Remove the washers and replace the tefloi washers (the factory procedure is a light wipl of hydrocarbon free silicone grease). Replace the stem assembly in the valve bod and tighten lightly. Push the washers down into the compressio: area in the same order as noted upon removal Replace the compression nut and tighten snus lY. Close the low pressure valve and fi l l the tan1 assembly. Check valves for leaks. Tighter again, i f necessary, and reassemble the unit.

REFILLER VALVE PACKING AOJUSTMENT Adjustment for me valve on the refiller can be madq

by loosening the set screw with a 3/32" hex key, so thz the handle turns freely on the stem.'lnsert two (2) 3/32' hex keys through the holes provided in the handle ant turn until they engage the holes in the packing adjuster Then tighten the packing by turning the handle.

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6.24 AIR SAMPLING SYSTEM MAINTENANCE 6.2.4.1 GENERAL

A potential problem associated with the OVA instrument is that leaks can develop in the air sample pump ing system. These leaks cad? ;esult in c i t h i r dilu:icn cr

tion x d slcw res;c,;s? :;::2.

6.2.4.2 TESTING FOR LEAKS The OVA's a re equipped with a flow gauge, which

provides a method to check for air leaks. Assemble the pickup probe selected for use to the readout assembly and then position the sidepack vertically so the flow gauge may be observed. Cover the end of the pickup probe with your finger and observe that the ball in the flow gauge goes to the bottom, indicating no air flow (i f ball has slight chatter while on bottom, this is accep table). Cover the center of the chamber exhaust port with your thumb and again observe the ball going to the bottom. Another simple check is to expose the pickup probe to cigarette smoke or a light vapor (butane) and observe that the meter responds in approximately 1.5 - 2.0 seconds. It should be noted that slow meter response may also indicate a restriction in the air sampling system.

6.24.3 LEAK ISOLATION Failure of the ball to go to the bottom when the inlet is

blocked indicates a leak in the system between the p r e be and the pump inlet or the inlet check valve. To isolate the problem, remove parts, one at a time, and again block off the air inlet. Remove the pickup probds) and cover the air inlet at the Readout Assembly. If the ball goes to the bottom, check that the "readout to probe" Seal washer is in place and replace the probes, holding them back against this seal while tightening the nut. Recheck, and if leakage is still present, it is probably in the probe (pickup fixture). which should be repaired or replaced.

If leakage is indicated as being past the readout handle when the connection to the sidepack is tight, dbconnect the sample line at the fitting on the sidepack and cover this inlet with your finger. If the flow gauge

!css ofsarnFln. -e , . C i l , - ' ^ ..., - : -J'-- : - .---...*- . - 7 . 1 . . - " 2 - - - - - . ,

ball goes to the bottom. the Problem should be a leak In the umbilical cordlReadout Assembly, which should be investigated and repaired. There is also the possibllity of a leaking check valve in the pump which would not show up cm thls test. If the lsakage is not found in the umbilical cord, it Is most likely In the pump check valve which should be repaired or replaced.

If the ball does not go to the bottom, the leak will be either in the flow gauge or it's connecting tubing. VlSuallY check that the tubing.is connected and if so, the flow gauge should be repaired or replaced. Check the "0" ring installation in the sample inlet connector (Fitting Assembly).

As an alternate approach, leaks on the inlet' side of the pump can be detected by using alcohol on a "0" Tip and lightly swabbing the connections one at a time or by directing organic vapor or smoke at the potent i leakage points and observing the meter response or audible alarm.

Leaks (beyond the pump) are easier to locate, as any of the commercially available leak detection solutions can be used. Cover the exhaust port, which will place the exhaust system under pressure, and check each connect!: 7 . zne z! 3 t i r , ~ . P.PP'?CS ?>g ???!on tubirg or

Check the igniter and Mixer/Burner Assembly where they screw into the detector, the high voltage terminal screw on the side of the MixerIBurner and exhaust port itself. If after these checks, the flow gauge ball still will not go to me bottom with the exhaust blocked, the prcr blem is likely a leaking exhaust check valve in the pump, which should be repaired or replaced.

rerzz= tr.2 ; : : ? z c ~ ~ ; ~ r ~ ~ ~ : ~ - , - : : .:;ita :sficz loini -:=.

6.25 CONTAMINATION CONTROL AND

6.2.5.1 GENERAL On occasion. the background reading of the OVA may

be relatively high under normal ambient conditions. Am- bient background readings will vary somewhat depen- ding on the geographical location where the instrument is being used. However, the background reading nor- malty should be in the range of 3 to 5 ppm as methane. The acceptable background reading consists of 1 to 1- 112 ppm of methane which is present in the normal air environment. In addition to the measurement of a normal methane background, there will normally be 2 to 4 ppm of equivalent methane background caused by acceptable levels of contamination in the hydrogen fuel andlor hydrogen fuel handling system resulting in a total equivalent methane reading of 3 to 5 ppm In clean air.

If the background reading goes above 5 ppm to 6 or 7 ppm. this is normally still acceptable since any measurement is additive to that background reading, i.e.. 2 ppm on top of 5 or 2 ppm on top of 7 provides the same differential reading. however, the lower background is obviously desirable.

The background reading on the linear OVA's is zeroed out or nulled out-even though in reality the background still exists. The background reading on the

MAINTENANCE

23

i m

linear OVA'S is measured by zeroing the meter with the flame w t and noting the meter-Indication after the flame - is on. However, on the logarithmic scaled OVA'S the background reading is observed on the meter at all times. Thls is considered desirable since it assures the operator that the instrument is, in fact, operating properly. m e background reading on the OVA'S serves as a low level calibration point since it does represent the measurement of ambient levels of methane in the air, which are extremely stable and predictable any place in the world.

The cause for a high background reading is usually associated wlth contamination in the hydrogen fuel system. Thls will. of course, cause a background reading since this is the function of the basic detector 'Yo measure contamination entering the detector chamber". In addition, contamination present in the hydrogen will many times leave a small unobservable deposit on the burner face which can continue to generate a background reading when the detector is in operation and the burner assembly is heated.

Another possible cause of contamination Is the mixerlburner assembly when the contamination is trapped in the porous bronze sample filter. This is not a common problem and usually only happens when an unusually high level of contaminant is drawn Into the assembly. Another possible cause of high background reading is contamination someplace In the air sample line to the detector. This is also uncommon but can be the source of the problem.

NOTE OVA'S that Include the Chromatograph Option installed can also have an indication of high background related to saturation or contamination of the actfvated charcoal filter. which Is in the line during chromatograph analysis, or of the Column which is in the hydrogen line at ail times.

6.2.5.2 ANALYSIS AND CORRECTION Prior to analyzing the problem, the OVA should be

checked tor proper electronic operation. Check logarithmic instruments for proper high and low calibration points and for proper gas selector operation (see Section 4). On logarithmic OVA'S, check Gas Selector by turning to 500 and observing the flameout alarm comes on as the needle goes below 1 ppm. It should be ensured that the instrument is calibrated to methane as referenced.

If, afterchecking that the OVA is properly calibrated, the background is still higher than normal for ambient conditions, the following procedure should be followed to Isolate the cause of the DrOblem.

Let the OVA run for a period of tlme (15 to 30 minutes) and see if the background level decreases as a function of time. The background could go down and stay down as a result of clearing line contarnination which is nmKnraMe simply by the normal flow of air through the sample line. Take a reading In a known, relatively clean air environment. Normally, outside air envlron-

ment is clean enough to assess by compariso - whether- the background- reading-Is-Internal t - the instrument or is present in the laboratop office or location where the instrument is bein used. If We OVA includes the Gas Chromatograph tion. depress the sample inject valve so that th activated charcoal is in the line and observ whether the background reading goes dow and stays steady after the elution of the a peak. The reading should always go down c 'stay the same but never be a highr background reading with the sample MIV depressed. since the charcoal filter will tak out any trace elements of organic vapors in th air heavier than a C2. if another activated cha coal filter is available, this may be attached t the end of the probe to scrub the air so that clean air sample would be going to the detec tor. The external activated charcoal can be u: ed on any instrument, with or withot chromatograph, for providing a clean air san ple to assess background level. If background still stays up and cannot t reduced by any of the previous steps, the saf. ty cover (if included) and the exhaust port c the detector chamber (Preamp Assembly) c the bottom of the case should be removed at the MixerlBurner Assembly scraped or brus ed wlth a small wire brush. (Referenc paragraph 6.2.1.3.) This will remove any smz quantities of contamination that are on the Mi erlBumer Assembly which could be the SOUR of the background vapor. After cleaning tt face of the burner and tube, replace the e haust port and safety cover (if included) ar reignite the OVA. If contamination on tt burner face was the cause, the problem shou be immediately resolved and the amble background will drop to an acceptable level.

5) If the background is still present, place yo' finger over the Inlet of the probe so as reduce the flow of air to the detector chambe Reduced flow rate may be observed either c the sample flow gauge or can normally t observed by the sound of the pump motor.

6) If the background drops immediately response to the reduced flow of air to tt chamber, this is an indication that the co tamination Is in the air sample line. Therefor. the various parts of the sample flow line suc as pickup probes, umbilical cord to the instr ment, etc., should be lnvestlgated by the pr cess of ellmination to see if the contaminatic can be Isolated. Serious contamination in the air sample line very uncommon. However, if very large dost of very heavy compounds are sampled. there a possibillty of a residual contamination whic would eventually clear itself out but may take considerable period of tlme. A typical cause f. the high background from me sample line is

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contaminated MixerlBurner Assembly. See paragraph (4) above for cleaning procedure. If heavy contamination of the MixerlBurner is still indicated by a high background, replace the MixerlBurner Assembly. In several OVA models, this will require removal of the Preamp Assembly. The old MixerlBurner Assembly should be either discarded or returned to the factory for cleaning and rebuilding. In the event there is contamination in the pump or other internal parts of the sample flow lines which cannot be removed, the sample flow components would have to be disassembled and cleaned. This is normally a factory type operation. However, the components such as the pump can be replaced in the field along with any contaminated tubing in the sample lines. High background readings on OVA's which include the Gas Chromatograph Option can be caused by other sources of contamination. If the charcoal in the charcoal filter mounted on the panel of the Instrument is contaminated or saturated, contaminated air would be supplied to the detector and raise the ambient level background. To check for this, the charcoal filtPr cartridse can bf! rsr?oved from the oanel and either a bypass tube put between the two connectors or the charcoal can be removed from the charcoal cartridge and the cartridge refilled with clean activated charcoal. This would determine i f the charcoal was the source of the background reading. It Is possible that an apparent high background reading could be due to contamination in the column that is on the instrument. This background could be caused by compounds that are slowly elutlng from a column which has become contaminated. The easiest way to check for column contamination is to replace the column with a known clean column or a short empty piece of column tubing and see if the high background reading drops. If all the above steps do not correct the high background problem, the cause wil l normally be contamination in the hydrogen fuel system.

Contamination in the hydrogen fuel system is usually the direct result of contamination in the hydrogen gas used or contamination introduced during the filling operatlon. Filling hose contamination can be caused by storing the hose in a contaminated area.

To remove contamination from the hydrogen fuel system, it should be purged with hydrogen. Effective purging of the hydrogen system is accomplished by disconnecting the capillary tube fitting which attaches on to the manifold block which has the low pressure gauge (H2 Supply Pressure Gauge and H2 Supply Valve). This disconnects the capillary tubing from the hydrogen line so that hydrogen may be purged at a reasonable rate from the tank assembly through the regulators, gauges and valves. After disconnecting the capillary, the hydrogen tank can be filled in the normal

manner. The tank valve and H2 supply valve can then be opened which will bleed the hydrogen from the tank through me H2 fuel system purging out the contamination whkh is in vapor form. There is the possibility that contamination has been introduced Into the hydrogen fuel system which is not readily purged out by the hydrogen gas but this is unlikely. Atter purging with clean hydrogen, approximately two or three times, the capillary tube should be reconnected and the backgrwnd again checked. Five of ten minutes should be allowed before assessing the background reading. since contaminated hydrogen may still have been trap ped in thecapillary tube.

If another tank assembly in a clean instrument is available, the fuel system from the clean Instrument can be connected to the contaminated instrument to ab- solutely verify that it is or is not in the hydrogen fuel supply system. The interconnection should be made to the capillary tube of the contaminated instrument.

6.2.6 FUSE REPLACEMENT This paragraph applies only to the standard (non-

certified) OVA's. There are two (2) overload fuses incorporated in the Battery Pack Assembly, one is a 3 A G 1 AXi? SIc-So in the power line to i,YS ;ump :nd isni:ar and the other a 3AG-114 AMP in the power line to the electronics. Soth iuses follow ;ae current iirnii1r.g resistors which provide primary short circuit protection. However, in the event of an excessive overload, the fuses will open and prevent overheating of the current limiting resistors. It should be pointed out that the 1 AMP S10-810 fuse will blow in approximately 8 to 12 seconds if the igniter switch is kept depressed. Normal ignition should take place in not more than 6 seconds. Therefore. do not depress igniter button for more than 8 seconds. If ignition does not occur, wait 1 to 2 minutes and try again. if the required 1 AMP Slo-Blo fuse Cannot be readily obtained, replace temporarily with a 3 AMP-3 AG standard fuse.

6.3 TROUBLE SHOOTING Table 61 presents a summary of recommended field

trouble shooting procedures. if necessary, the instru- m t can be easily removed from the case by unlocking the four (4) 114 turn fasteners on the panel face and removing the refill cap and exhaust port. The battery pack is removed by taking out the four (4) screws on the panel and disconnecting the power connector at the battery pack.

6.4 FACTORY MAINTENANCE To ensure continuous trouble-free operation, Century

recommends a periodic factory maintenance, overhaul and recalibration. The recommended schedule is every six (6) to nine (9) months. This maintenance program includes replacement of plastic seals and parts as r e quired, pump overhaul, motor check, new batteries, sample line cleaning, H2 leak check, recalibration, replacement of plastic hose as required, and detailed examination of the unit for any other required maintenance and repair.

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The recommended procedure for malntenance and repair beyond the scope of this manual is to Send the complete instrument or subassembly to the Century factory for repairs. m e assemblies will be handled ex- peditiously for rapid turnaround.

8.5 FIELD MAINTENANCE Although not recommended, where field

maintenance beyond that described herein is considered essential, the assembly drawings, parts llsts and schematics in Appendix "A" will be of assistance.

6.6 RECOMMENDED SPARES Century does not recommend that spares be main-

tained for its instruments. However, if the instrument Is to be used in a remote area or spares are desired for other reasons. the following list should be used as a guide.

RECOMMENDED SPARES

NOTE: Unit q u a n t i t y i s each u n l e s s otherwise noted.

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' 7.1 GAS CHRoMATOkRAPH (GC) OPTION 7.1.1 INTRODUCTION

The Century Portable Organic Vapor Analyzers (OVA's). when used as described in the previous sections of this manual. are very efficient and accurate indicators'of total organic compound concentrattons on a continuous sampling basis for a period of eight (8) hours minimum and with a response time of one to two seconds. However, in areas where mixtures of organic vapors are present, it often becomes necessary to determine the relative concentration of the components andlor to make quantitative analysis of specific compounds. .

To provide this additional capability, a built-in gas chromatograph (GC) system has been added as an option to the OVA series of instruments. See Figure 7-1-1 for the location of the major components and controls associated with the GC Optlon. When the GC Option is used as described in this section, the capability of the OVA will include both cualitative and on-the-spct qu-ln- titative analysis of specific components present in the ambient envircnmsnt. Tke Strip Char: Recorder cp:izn, which is used with the GC Option, is described separately in paragraph 7.2.

This section is appllcable only to OVA's with the optional gas chromatograph system. it is recommended that this entire sectlon be read, along with the corresponding sections of the basic Operating and Service Manual, prior to operating the instrument.;

7.1.2 DESCRIPTION AND LEADING PARTlCULARS 7.1 -2.7 GENERAL

When the GC Option is installed on a Century OVA, the OVA will have two modes of operation. The first mode is the measurement of total organic vapors in the same manner as described in the basic operating manual for the OVA instrument. This mode is referred to as the "Survey Mode". The OVA will be in the "Survey Mode" of operation whenever the Sample Inject Valve is in the "out" position.

The second mode of operation is called the "GC Mode". The OVA Is in this mode of operation any time a sample has been injected into the GC system and the sample is being transported through the GC column. This section provides a brief description of how a gas chromatograph (GC) operates and specifically how the Century instruments perform the required operations. A complete, comprehensive discussion of gas chromatography theory, column selection and data analysis is beyond the scope of this manual.

It should be pointed out that the GC Option was designed to extend the capabilities of the Century OVA as a field type instrument. A "field type" instrument as used herein is defined as a fully portable, self- contained instrument capable of making direct on-site analysis of organic vapors in air. The OVA with GC Op- tion can be utilized for many types of analysis in the out- door or indoor ambient environment or for specific

e.

laboratory type analysis. m e OVA was not designed to compete with the- research -or -process -type gas - -

chromatograph but to compliment these instruments or elimlnate their need in field type applicattona

mls manual is intended to provide an operator wtth sufficlent information to operate and maintain the Can- tury instrument. Century further publlshea Applica- tlonlTechnical Notes to assist the operators in applying the instrument to actual field monitoring situations. The criteria for the design of the GC Option was the same as the basic OVA, that is. simplicity, ease of operation, high reliability, field ruggedness and minimized potential for operator error.

7.1.2.2 PWNCIPLEOF OPERATION a) GENERAL

For those not specifically trained or familiar with gas chromatography, the technique employed in the OVA during GC Mode operation is basically a separation of components in a sample gas contacted with the material in a column. When non-interference can be achiev- ed, each component of the sample mixture e t ~ ; a s from i h e column sics4y into the flame ionization detector chamber to orovide its own measurable response on f i e meter and recorder. When used as directed in this manual, the GC Option can drastically reduce and in most cases eliminate the need for elaborate grab sample and laboratory analysis techniques and the analysis can be made on- the-spot at the point of interest. All flame ionization detector (FID) gas chromatographs require certain elements for their operation. These elements indude three flow regulated gas supplies as follows: 1) A carrier gas (normally nitrogen or helium) to transport the sample through the columns; 2) Hydrogen gas for operation of the FID; 3) A dean air or oxygen supply to support combustion of the FlD. In addition, a method for injecting a known volume of sample air (aliquot) to be analyzed is required. In standard as chromatographs these three (3) flow regulated gases are individually supplied from pressurized cylinders equipped with regulators and flow control apparatus. The Cen- tury GC system differs in that the hydrogen (H2) fuel for the FID is also used as the m e r gas. The clean air supply is simply the m a l air sample pumped to the FID. But, during GC analysts, the air is scrubbed in a charcoal filter to provide a clean air supply. The end result Is that no a d d i i gas supplies are requlred to adapt the GC Option to the basic OVA instrw ment A W n g arrangement is incorporated to provide a method for transferring a fixed vdume of

. the air normally being pumped to the Fill in the Survey Mode into the GC system for analysis. The sample air injected into the GC system is

the same sample being analyzed by the OVA for total organic vapor concentration. Therefore, the instrument provides the unique capability to observe the total organic vapor concentration of the sample prior to injecting it into the GC system. This operating feature is invaluable in fieM work where the environment is continually changing and where valuable GC analysis time must be exp$nded only on the samples of concern.

Figure 7-1-2 is a flow diagram illustrating the flow paths of the hydrogen (H2) fuel, sample air supply and GC injected sample aliquot. There

- are two push-pull valves used in the GC system, the Sample Inject Valve and the Backfiush Valve. Block D of Figure 7-1-2 illustrates the flow paths with the Sample Inject Valve in the “Out” position which leaves the OVA In the Survey Mode. With this valve in the “out” position. the OVA will function in its normal manner as a total organic vapor analyzer. Block C of Figure 7-1-2 illustrates t > l flow pa!hs after the Sample Inject Valve is moved to the “in” position to initiate the GC Mode. It can be observed that the hydrogen flow path is now through the sample loop which enables the hydrogen to sweep the air sample from the loop and carry it through the GC column. It can also be obseerved that the sample air going to the FID chamber is now muted through the activated charcoal filter where essentially all organic vapor contamination Is removed from the air. The activated charcoal filter will effectively ad- sorb most organic vapors with the exception of methane and ethane. The functions of the Sam- ple Inject Valve are, therefore, to transfer a fixed volume sample of the air being monitored in- to the hydrogen stream and to reroute the sample air supply through a Rlter (scrubber). The Backflush Valve has no prepositioning r e quirement to function. tt can be in either the “in” or “out” position at the time a sample is injected into the GC system for analysis. The Backfiush Valve simply reverses the direction of the hydrogen flow through the GC column. If the Backflush Valve is in the “out” position during sample injection and analysis, it is simp ly moved to the “in” position when backflushing is desired or vice versa. See blocks A and 6 of figure 7-1-2. It should, be noted in Figure 7-1-2 that hydrogen is always flowing through the column and onto the flD detector and that the sample air supply is always flowing to the FID detector to provide oxygen for the hydrogen flame regardless of me aperating mode. The recommended H2 flow rate is 12 cclmin. for praper FID operation and as a standard flow rate for generating GC referemelcalibration

b) SAMPLEFLOW

data. This H2 Row rate is adjusted by varying the H2 Supply Pressure, which is the hydrogen pressure at the input of the flow control capillary tube of the OVA. The pressure is changed by adjusting the set screw in the bon- net of the low pressure regulator, accessible by removing the battery pack from the instrument panel. To monitor the H2 flow rate, connect a bubble meter to an end of the GC column which has been disconnected from the panel fitting and move the Backflush Valve so that hydrogen is flowing out of the column. Primary H2 flow control is accomplished by the capillary tube 01 the OVA. However, the flow restriction of a GC column will also affect the H2 flow rate and the effect will vary with column length, type 01 packing and packing methods. The nominal HE Supply Pressure is around 10 PSIG and the pressure drop across a typical 24 inch long column packed with 60180 mesh material is a p proximately 1 to 1.5 PSIG. Normally, whentht H2 flow rate is set at 12 cclmin. with a Centup standard 24 inch long column, no adjustmen needs to be made when using columns fron three (3) inches to four (4) feet long. Longer col umns may require H2 flow adjustment for prc per operation. Adjustment would be required i and when precisely controlled analysis was be ing conducted or when the hydrogen flow wa. too low to keep the flame burning. m e sample air flow in the OVA is not adjustablc and is nominally 1 .O llterlminute. This flow rate should remain relatively constant. A Sarr ple Flow Gauge is provided on the OVA panel 1. monitor the sample flow rate. (NOTE: Pan€ gauge is not calibrated in LPM.) When the Sam ple Inject Valve is in the “in” position, thert may be a slight increase or decrease in sampl air flow rate (0 to 15%). This change will norma. ly not affect operation of the instrument as lone as the flow rate is consistent from analysis t analysis. Basically, i f the sample air flow rate i consistent between calibration and end usage there will be suitable precision in th measurements. GC ANALYSIS 1) Sample Injection

When the Sample Inject Valve is depres: ed. the small volume of the input air sampl which is in the sample loop is injected intc the hydrogen stream which transports th sample through the column for separatio of its components and on to the flam chamber for analysis. This small volume c injected sample is, therefore, qualitative1 analyzed based on the retention time of th individual components of that sample whil passing through the column. Quantitativ analysis can then be accomplished by pea height or peak area analysis methods.

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3959 The'Column The column consists tubing Dacked with -a -material which physucdly interacts-with the organic vapors in me air sample in a manner which slows Qorn the passage of the vapors through the column. Since the packing material has a different attraction for each individual orgprmw: substance, each component in a mixtum of gases will be slowed down to a dnterent extent when passed through the cahnnn. The net effect is a separation of the gases in such a way that each component eMes from the column at a different -. The individual gases are then autammtically fed to the detector which gives a response to the meter or to an externat! strip chart recorder. For example: Suppose that a sample containing benzene and to&ene is injected on- to the column containang appropriate packing material. As illustrPed in Figure 7-1-3, a portion of the benzene and toluene are ad- sorbed on the pac%nrg material. The a r c ~ n * s involvod d ~ r e - < s on tbe relativs

.-.a:eri:l. Tk? zz;icer as r t i c ~ . ? ~ the g&eous phase iorward a short distance, and since benzene will have less affinity than does toluepre. it will be moved through the column more readily and thus a separation of these two components takes place and benzene reaches the detector at the exit of the column fsrst

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3) Qualitative Analysis As each organic substance has a-unique in-

.- t6fSctii5n wiih the column packing material. the time that the substance Is retained on the column is also unique and thus characteristic of that particular substance. The !'retention time" (RT) is primarily dependent on the type of packing material, the length of the column, the flow rate of the gas carrying the mixture through the column and the temperature range of the system. When these variables are controlled. the retention times can be used to identify each of the components in a mixture. Because of these variables, it is usually necessary to establish retention times for each instrument by making a test with the, pure substances of interest or to refer to established time data charts prepared in advance for that specific instrument. In those cases where retention times of the components are too close together for a good analysis, an adjustment in one or more 0: !he coeratirq variables will effect a suffiti$,7i ci:i-.r;.ncs :n r+tSni;cr; ;ir;4s to enable meaningful analysis.

The response of the detector to any component after it has been separated by the column is proportional to the quantity of organic material passing through the detector at any given time. However, since

4) Quantitative Analysis

BENZENE & TOLUENE /-COLUMN

TO DETECTOR

"A"

y TOLUENE BENZENE

DETECTOR RECORDER TOLUENE , r, 7

BENZENE TOLUENE

"C"

PICTORIAL SEPARATION OF BENZENE AND TOLUENE - "A" A T B m O F SEPARATlON; "9" DUIUNG SEPARATION; "C" BENZENE HAS ALREADY PASSED THE DETECTOR AND IS RECORDED. TOLUENE (DOTTED LINES) WLLL APPEAR ON RECORDER s IT PASSES THE DETECTOR.

FIGURE 7-1-3, TYPICAL COLUMN SEPARATION SEQUENCE

. . . t . .

not all of the separated components elute from the column at the same instant, but varies from low to a maximum and then falls to ambient again, it is necessary to have a means to measure the total amount of the individual component vapors. When using a strip chart recorder, the curve drawn on the paper is triangularly shaped and the area under the peak is related to the amount of substance being analyzed. For the OVA systems which have logarithmic outputs, direct measurement of areas under the peak is extremely difficult. The Inethods of peak height analysis described herein provide a convenient means for CtUantitatiVely interpreting peaks when operating either the logarithmic or linear readout OVA'S. Backflush The column Backflush Valve is provided to reverse the flow of the carrier gas (hydrogen) through the column. It is necessary that the column be backflushed after each individual analysis except under certain special conditions. The primary purpose of the backflush function is to clear the column of heavy compounds (with long retention times) which would con- taminate the column and cause interference to the total organic reading and future GC analysis. The Backflush Valve has no "sense" (prepositioning requirement). It is simply reversed from either position it was in during GC analysis. The Backflush Valve should be actuated immediately after the peak of the last corn- pound of interest elutes. Figure 7-1-2 illustrates the functions of the Backflush Valve. In the Century GC system, the backflush is "to the detector". This is possible due to the fact that the carrier gas and detector fuel are one in the same, i.e.. hydrogen. The backflush function, therefore, provides a convenient means of quantifying the total compounds in the backflush by simply, recording the peak that elutes during the backflush operation. For field type instruments, this quantitative backflush information is very valuable. The backflush to detector also provides a direct means of observing the condition of the column and seeing when the column is clean and the detector response has returned to baseline. The time required for the backflush is usually 1.2 to 1.5 times the GC analysis time. Survey to GC Mode Interface There is an inherent advantage to in- tegrating the GC system to the basic total Organic Vapor Analyzer (OVA). The OVA provides a direct reading of total organic vapors present in the air being sampled,

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which provides the operator with intelligence of what he is injecting into the GC system. He can then use this information to predict and verify the peaks that result during the GC analysis, Including the backflush peak. This feature completely eliminates expen- ding valuable GC analysis time where there is no contamination concentrations of con-

1 cern (comparable to taking noise measurements in quiet corners). This "front end" intelligence also enables the operator to select the most appropriate IOCatlOn to conduct an analysis, which is normally the area of highest concentration.

7.1.3 OPERATlNG PROCEDURES 7.1.3.1 GENERAL

The Gas Chromatograph (GC) Option is a supplemen- tary system which is built into the OVA instrument during manufacture. This system provides an additional gas chromatographic anaiysis (GC Mode) of operatlon which can be initiated at any time during a survey by simply depressing the Sample Inject Valve. After com- pletion of the anaiysis and backflush operations, the Sample Inject Valve is pulled out and the survey con- tinued or another sample injected. Note that when the Sample Inject Valve is in the out (Survey Mode) position the OVA operates in . the same manner as a standard OVA which does not incorporate the GC Option.

7.1.3.2 Refer to Figure 7-1-1 for a view of the four (4) basic

controls and system components provided in the GC Option. Table 7-1-1 below describes their functions.

GC SYSTEM CONTROLS AND COMPONENTS

TABLE 7-1-1 GC OPnON-COMPONENTS

Controlsllndlcators - Functlon Sample Inject Valve - This 2 position valve (showfl schematically in Figure 7-1-2) is used to select either Survey Mode (valve out) or GC Mode (valve in). Backflush Valve - This 2 position valve (shown schematically in Figure 7-1-2) is used to reverse the flow of H2 through the column to:

a) Backflush the column for clearing b) Quantitatively measure total compounds after a selected point. Example: Separation of methane from non-methane hydrocarbons to read total non-methane hydrocarbon level.

Column - Separates components of a gas mixture so that each component of the mixture elutes from the column at a different time. Activated Charcoal Filter Assembly - This assembly functions only in the GC Mode (Sam- ple Inject Valve "in") as shown schematically in Figure 7-1-2. It removes organic compounds (except simple Ciand C2 hydrocarbons) by ad- sorptlon from the sample air supply.

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-IC""C~NG AND TURN ON Place the Sample Inject Valve in the "out" position-

and put-the OVA instrumenfin operation per-s-iction 2 of this manual. NOTE Leave the hydrogen fuel and pump "on" for three (3) to four (4) minutes before at- tempting ignition to enable hydrogen purging of the column.

7.1.3.4 SURVEY MODE OPERATION When using the OVA in the Survey Mode, ensure that

the Sample Inject Valve remains in the fuli "out" position and that the Backflush Valve is either full "in" or full "out". Note that when changing from the GC Mode to the Survey Mode the OVA output readings will continue to change as long as any compounds are still eluting from the GC column. Therefore, under normal field conditions, the GC column should be backflushed for clearing, which takes approximately 1.2 to 1.5 times the already elapsed forward analysis time. The backflush peak may be observed returning to baseline, after which the Sample Inject Valve may be moved to the Survey Mode (out) position.

When the compound(s) being analyzed are known to be tne only ccmpound(s) present in :he air sample, backflushing may be omitted.

7.1.3.5 GC MODE OPERATION In normal GC analysis. a strip chart recorder is used

to record the output concentration from the OVA as a function of time. This record, called a chromatogram, is utilized for interpretation of the GC data. The Century portable strip chart recorder is further described in paragraph 7.2.

a) OPERATION Turn on recorder and push Sample Inject Valve "in" with a fast, positive motion. This starts the GC analysis which is automatic up to the point of backflushing. NOTE: Rapid and positive motion should be used when moving either the Sample Inject or Backflush Valves. On occasion, the flame in the FID detector may go out. which would be Indicated by a sharp and con- tinued drop of the concentration level. If this occurs, simply reignite the flame in the normal manner and continue the analysis. NO= A negative "air" peak typically occurs shortly after Sample injection and should not be confused as flame-out. The negative air peak and various positive compound peaks will be indicated on the OVA readout meter and the strip chart recorder and represent the chromatogram of the analysis. After the predetermined time for the analysis has elapsed (normally immediately after the peak of the last compound of concern). rapidly move the Backflush Valve to It's alternate position (In or out). Leave the Instrument in this condltion until the. backflush peak' printed on the recorder returns to baseline, then pull the Sample

3 3.5 9 Inject Valve to the "out" position. If no

. backflush peak appears, pull the-Semple - - -

Inject Valve out after being in the backflush conditlon for a period at least as long 85 the analysis time. The OVA Is now back In the Survey Mode and ready for survey use or Injection of another sample Into the GC system.

Interpretation of the recorded chromatogram is always based on predetermined calibration data. A discussion of calibration methods and chromatogram interpretation is presented in paragraph 7.1.4.

b) INTERPRETATION OF RESULTS

7.1.4 CALIBRATION 7.1.4.1 GENERAL

The Century OVA with GC Option is a field instrument intended for applications where there are a limited number of compounds of interest and the compounds are normally known. Under these field conditions, the operator must simply know the retention time and peak height characteristics of the compounds of interest as norrnaily presented on nis OVA instrument under his specific operating ccnditions. Therefore, to calibrate ;ne CVA in the GC M&P. simply determine oy test tiie retention time and peak area (using peak height analysis) characteristics for the compounds of concern. These tests should be conducted on the column to be utilized and over the concentratlon and temperature range of concern. When representative characteristic 'data is available, such as in the Century Applica- tionliechnical Notes, a spot calibration check is normally all that is required.

It should be noted that under normal field conditions, the vapor concentrations vary continually as a function of time, location and conditions. Field measurements for industrial hygiene work are normally associated with a threshold level around a preestablished concentration. Surveys for locating fugative emission sources present a continually varying situation. Under these typical field conditions, it is desirable to have a fast and simple method of interpreting the GC data for on-the- spot analysis and decisia.n maklng. High precision is normally not a requirement for these type analysis since the environment is continually changing. The methods presented in this section are designed to provide a means for typical field analysis. When the OVA is used under laboratory conditions, standard laboratory methodology may be used for greater precision.

7.1.4.2 TECHNICAL DISCUSSION The chromatogram is a strip chart recorder printout of

the Instantaneous organic vapor concentration from the Century Organic Vapor Analyzer (OVA) as a function of time. A typical chromatogram is illustrated in Figure 7-1- 4 and is seen to be a series of triangular shape peaks orlginating and returning to a fixed baseline. Oualitative interpretation of a chromatogram involves identifying the compound causing a peak by analyzing the time it took for the peak to appear after initlal injection (referred to as retention time (RT)) and comparing this RT to

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reference data. Quantitative interpretation of a peak involves analyzing the area under the peak and relating this area to calibration data of peak area versus concentration for that specific compound under the conditions present during the GC analysis.

It can therefore be seen that interpretation of a chromatogram requires the use of calibration reference data. GC reference data is always generated empirical- ly, i.e.. through .tests. Century publishes Applica- tionlTechnical Notes which may be used as a reference for selecting columns and interpreting chromatograms. However, in most cases, certain relatively simple tests must be conducted to obtain the required reference data. A method for obtaining this type data and applying it to a calibration chart is presented along with a typical example of the exercise.

QUALITATIVE ANALYSIS Under a given set of operating conditions, the retention time is characteristic of that particular substance, and can be used to identify specific compounds. It will be necessary to calibrate retention times by making tests with the pure compounds of interest. The retention time (RT) is defined as that period of time from injection of the sample into the GC system until the point of maximum detector response for each substance. Retention time is measured from the point of sample injection to the apex of the triangle shaped cuwe obtained on the stripchart recorder. (See Figure 7-14.) The strip chart recorder operates on a clock mechanism such that the distance along the baseline is proportional to time. While retention times are characteristic for each compound, it is possible that two materials could have the same retention times. Thus, if there is any question as to the identity of the vapor. it may be neceSSary to verify identification by retention times on two different columns. Use of a longer column will increase the retention times of those components it is capable of separating. The time between peaks will therefore also be increased. This is especially useful to know if a component to be studied comes through too fast after injecting a sample or if certain desired peaks are so close that they overlap on the strip chart. COLUMN SELECTION Two cdumns are normally supplied with the instrument. These are general purpose columns and are useful in a wide variety of applications. If they do not perform the separations for your particular application, it may be necessary to select other packing materials or lengths of columns to meet your needs. Century Systems will guide you in this selection or prepare a custom column to meet your needs. If columns are made by the customer 01 purchased from other sources. care must be exercised to ensure that their packing density does not create too large a pressure drop as com-

pared to columns furnished by Century. Cen- tury’s method of coding it’s GC columns is presented on most Century published Applica- tionlTechnical Notes. Several application notes have been inserted as an appendix to this manual to illustrate typical GC separations. TEMPERATURE EFFECT ON RETENTION TIME An increase in temperature will decrease column retention time (RT) and vice versa. Normal- ly, retention time (RT) as a function of temperature changes linearly over the range of 0 to 40%. For complex qualitative analysis, a calibration plot of RT versus temperature will be required. In typical ambient field usage such as inside a factory, the effect of temperature can be compensated for by the operator during chromatogram interpretation. A single component tracer compound can be sampled at any time to provide a “key” for other compound identification. CARRIER GAS FLOW RATE EFFECT ON RETENTION TIME An increase in carrier gas flow rate will decrease retention time. For reproducible data. the carrier gas (hydrogen) flow rate must be , recorded in association with a chromatogram. Primary control of the H2 flow rate is accomplished in the OVA by regulating the hydrogen pressure across a capillary tube. The hydrogen flow rate is also affected by the restriction of the GC column but most column5 have a limited effect. The hydrogen flow rate is factory set at 12 cclminute with a typical 24 inch column. QUANTITATIVE ANALYSIS The area under a specific peak is a function 01

the concentration of the compound which created the peak. This area can be calibratec by injecting known concentrations of the compound. When the base of a symmetrical GC peak remains constant, the height of the peak may be used to measure the area. Typically, as the retention time of a peak increases on the same column, the base broadens and the peak height decreases for a given sample concentration. If the hydrogen flow rate is considered tc be constant, the retention time of the peak wilt change as a function of temperature. In general, the more triangularly symmetrical the peak, the better the peak height analysis capability. However. many GC peaks have “tail- Ing” as illustrated in Figure 7-14. Peak height calibration is still an acceptable method for quantitative analysis as long as the area under the tail is small compared with the total peak area. If severe tailing occurs. empirical calibration data generated through tests may be required to plot the peak height versus the concentration cuwe. tf me GC Option is used on a Century “logarithmic” OVA, there will be a ma- . lor apparent Increase in peak talling. This a p parent tailing b the result of the logarithmic

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scaling, which amplifies the low tevel signals. This apparent tailing does not appear on the “linear” OVA’S. even though the same actual tailing is present. Only peak height analysis will be discussed in this manual. The method presented is simply to inject a known concentration of me compound being tested and record the height of the peak under the test conditions. The peak height characteristics can be established for various columns and at various temperatures. Normal- ly, both retention time and peak height characteristics will be measured simultaneously during the same test. When peak area measurements are desired, the areas may be measured using an integrator on the OVA output signal. Other mar)ud methods may also be used, such as couhting squares, weighing cuwes or simple triangulation. When the GC peaks have good symmetry, triangulation (area equals 112 base x height) is a convenient method.

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7.1.4.3 PREPARATION OF CALIBRATION SAMPLES Samples for calibration of the GC system may be

prepared with the procedures discussed in paragraph 4.3.3 of this manual. Sample mixtures are made by repeating the procedures presented for the compounds desired in the sample.

7.1.4.4 CALIBRATION DATA When conducting tests to obtain GC calibration data,

the following information should be recorded to qualify the data:

a) Column - description and serial number as a g plicable

b) Temperature - column temperature, normally room ambient

c) Chart speed - distancelunit time d) Carrier flow rate - hydrogen flow rate through

the column (cclmin.). (Reference paragraph 7.1.2.2 b)

e) Sample concentration - ppm for each compound

1 ) Sample volume - OVA by serial number or typically 0.25 cc for standard valve

9) Recorder scaling - ppm per unit deflection h) Range - range of OVA being used, i.e.. X I , X10,

Xloo i) OVA type and serial number

To obtain a calibration point, inject a known concentration sample into the GC system and record the resulting chromatogram peak. The retention time for the peak may be scaled from the record or timed with a stop watch. The peak height may be scaled from the record or the OVA readout meter may be observed during the elution of the peak. Figure 7-1-5 presents the for- mat of a chart which may be used to record calibration data. Experience has indicated that the peak height response of a compound is linear up to concentrations

of greater than 1,OOO ppm. Therefore, a single calibn tion point. preferably around the concentration of mo: concern. is normally all that is required to plot a pea height response in ppm as a function of compound cor centration. Data for other compounds on the same co umn may also be plotted along with their associatet retention times, percent relative response in the tot; organic Survey Mode, TLV. etc. Note that to keep th. calibration curves readable on the chart a multiplier (X column is included. It is recommended that copies c the actual chromatograms be kept with the charts fo observing the peak shapes, peak interferences, etc. I should be noted that a chromatogram can be utilitec like a fingerprint for compound identification or peal height and shape comparison. Transparent overlays art sometimes an aid in chromatogram analysis.

When temperature variations are anticipated, data should be taken at several points and recorded on the chart as a new curve or as a relative change as a function of temperature as illustrated in Figure 7-1-5.

Preparing and using the calibration chart is very straightforward. As an example, once the elution sequence of a group of compounds is determined, a mixture of 100 ppm of each can be prepared and run on the GC for chart data. The retention time of each compound and the peak height of each can be read directly from the chromatogram and the data put on the chart. If temperature data is to be taken, additional chromatograms may be run with the same sample and the RT and peak height plotted as a function of temperature.

When complex mixtures such as gasoline are analyzed, it may be desirable to keep the record of the backflush peak for future reference and peak area com- comparison. It is also recommended that the total - organic vapor concentration reading on the OVA be recorded for each calibration sample used. This reading should be put on the chromatogram and is used for ar- riving at relative response numbers and as a check on sample preparation precision.

Samples of forms for use in recording individual chromatogram data and also a sample form for the calibration chart are included in Appendix “A” and may be used as a guide or copied and used as is.

7.1.5 MAINTENANCE 7.1.5.1 GENERAL

This section describes the routine maintenance, trouble shooting and spare parts peculiar only to the Gas Chromatograph (GC) Option.

7.1.5.2 ROUTINE MAINTENANCE a) COLUMN

Any column can be contaminated with compounds having long retention times. This will result in high background readings. This condition can be checked by installing a new column or a blank column (tubing only). If this reduces the background reading, the contaminated column should be baked at 1OOOC (2l2OF) for three (3) to four (4) hours in a drying oven while passing nitrogen through the column. Higher

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while installed on the OVA by heating the column with hot, wet towels. When installing any column, avoM touching the ends, as this may cause contamination. Also, ensure that the fittings are tight to avoid H2 leakage. IMPORTANT: The following simple test may be run to determine whether the GC column is contaminated. While in a clean ambient air background, place the Sample Inject Valve in the “in” (GC Mode) positlon. Observe the background reading on the meter or recorder. After one (1) to two (2) minutes. change the position of the Backflush Valve and again observe the background reading. If the background reading went down when the Backflush Valve was actuated and then started to increase in one (1) to two (2) minutes, the column is probably contaminated and needs to be cleaned. Note that if hydrogen is flowing into one zrd of the Sclcmn !cr a period of time, !h? ccc’z-lnation is holng xs?erJ into the column and is :hPrefore cleming the frofit andDorticn of the coiumn. Then when the hydrogen flow IS reversed, the exhaust end of the column will be what was the input end previously. Therefore, for a period of time the now exhaust end of the column will be clean until the contamination is again pushed through. Remember that to clean a column the hydrogen or other purge gas must be run through the column in one direction until all of the contamination is removed. NOTE: Contaminated columns can be avoided by simply backflushing the column after every analysis. CHARCOAL FILTER ASSEMBLY After repeated use, the Charcoal Filter Assembly will become saturated. Periodically, the operator should check the effectiveness of the activated charcoal to perform its screening function. This can easily be done by operating the unit with the Sample Inject Valve “in” and passing the probe near a concentrated sample of the compounds being analyzed. The readout should remain nearly steady (should not rise more than 0-2 parts per million (ppm)). If rise is more than 2 ppm, remove assembly from the panel and pull the knurled cap from me end of the filter tube (pull-not twist). and replace the old charcoal with activated charcoal (Barnebey Cheney, Columbus, Ohio, Type GI or equivalent). Care should be taken to completely fill the tube so there will not be a path for the sample to bypass the charcoal. The life of me charcoal depends on the time (length) of exposure and the concentration level during that exposure. When changing charcoal, be sure that any fine particle charcoal dust is removed from the assembly.

Another simple test of the charcoal filter is to note the background reading with the Sampte- - -

Inject Valve “out” and then note the baseline reading with the valve “In”. The level should never be higher when the valve is in the “ln” position and the charcoal fllter is in the air line. If the reading with the valve in the “in” position is higher, the charcoal filter is probably contaminated and acting like a contamination emit ter.

Characteristics of the recommended activated charcoal are provided below:

Raw Mat-: Coconut Shell Nomlnel Mesh Slze: 8 x 14 (Tyler Standard Screens) &e Dlstrlbutlon: On 8 mesh, 5% maximum:

through 8 on 10.60% maximum; through 10 on 14.60% maximum; through 14 mesh, 5% maximum

Ash: 6% maximum MdSturt3 Content: 3% maximum, as packed Standard Packages: 50 Ibs. net weight fiber con-

tainer: 58 Ibs. gross wetGht (typical). 1 Ib. con- tainer, ShiDping weight aporoximately 1-1 12 i s ~ . L. b o ~ ccniz,n,;.g I _ ?z;h i ib. units. snipping weight approximately 16 Ibs.

Applicatlons: Removal of medium and high conceo- trations of organic vapors from air. Purifica- tion of gases. Safety respirators. Gas separation.

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7.1.5.3 TROUBLE SHOOTING Table 7-1-2 presents recornmended field trouble

shooting procedures which are peculiar to the GC system. These procedures are In addition to those found in Table 6-1 of the basic manual.

7.1 -5.4 RECOMMENDED SPARES Spare parts and supplies which are recommended to

support only the GC system (and recorder) are as 0

follows: Item Description QlJ-tHY Part Number 1) Quad Rings 5104961 (1Olpkg.) 1 pkg. 2) Tubing, Teflon .148“ ID x -020 wall 12” 3) Tubing, Teflon -120” ID x .WO wall 12”

5) ”0” Ring 2-1 5 2 4) Activated Charcoal Type GI or equivalent 1 Ib.

6) Chart Paper (log) Type “J” (6 rls.lpkg.1 2 pkg. 7) Chart Paper (linear) Type “WA” (6 rls./pkg.) 2 pkg.

Activated charcoal may be purchased direct from: Bamebey Cheney 825 North Cassady Columbus, Ohio 43219 (6l4) 2584501

Chart paper may be purchased direct from: Gulton Recorder Systems Div. Gulton Industrial Park East Greenwich, Rhode Island 02818 (a)- - -

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7.2 RECORDER OPTION 7 . 2 L GENERAL - - - _- - - -_ - - - - - - - -

1 A Portable Strlp Chart Recorder Is available from Cen- tury for use with me OVA Instruments (reference Figure 7-2-1). The recorder is powered from the OVA battery pack and the output can be scaled to match the OVA

I readout meter, thereby providing a permanent record for subsequent analysis or reference. m e recorder Is avail- in two models. PIN 5104451 is used with standard Models OVA-88,OVA-98 and OVA-118. PIN 5104452

1 is certified intrinsically safe and is used with the certified Models OVA-108,OVA-128 and OVA-138.

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B Input signal E pes. 12VDC input H Ground

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7.2.5 opERAnffi PROCEDURES Connect cable between recorder and OVA. Turn

?&order oKbjis&i3ktlng either the HIGH or-LOW p0SK tion of the switch. (Normal is "LOW".)

When using the HIGH gain position (typically only on logarlthmlc OVA'S). it may be desirable to "null" out the background on the recorder. To accomplish thls. provide clean air to the OVA or place a charcoal filter in line with the OVA input to establish a "zero" reference and use the ZERO ADJUST Knob to set the recorder needle to the zero line. Remove the Rlter and the instrument and recorder are ready for use. NOTE: During normal survey use. it Is best to turn the recorder off to conserve paper and battery power.

7.2.6 CALIBRATION 7.2.6.1 GENERAL

Electronic and mechanical adjustments, other than the operational adjustments on the side panel. are provided to calibrate and align the recorder.

7.2.6.2 MECHANICAL ZERO ADJUSTMENT a) Snap out the front panel nameplate (using a

small b!ade screwdriver in t h e le?? hand slot) for --,.---. .T - - -L--:c-l 1 '"73 - - ha2r-!--Z1;J 5 .,,:a> In b , - o - 2'351::Cil.

b) Unscrew knurled fastener at top left of front panel, open recorder. Pull down plastic chassis latch on right side to release sticker bar tension on paper and adjust mechanical zero as required. Replace nameplate, chassis latch and resecure front panel.

7.2.6.3 GAIN ADJUSTMENT Separate adjustments are provided for the HIGH and

LOW ranges on the recorder. (Refer to Figure 7-2-1 for location.)

a) Connect recorder to OVA and adjust OVA for full scale reading on readout (about 5 VDC).

b) Loosen knurled fastener on upper left of the front panel and pull front panel down.

c) Place HIGH-LOW Switch in LOW and adjust Rl until recorder prints full scale.

d) Place HIGH-LOW Switch in HIGH and adjust OVA to read the desired full scale with front panel CALIBRATE ADJUST Knob, typically half scale on the readout. Adjust R2 until recorder reads full scale. NOTE: Full scale adjustment of the recorder for 112 scale on the OVA gives a gain increase of two (2) in the height of the peak on the chromatograms. This is the factory set point for the HIGH gain range: however, other points can be set as desired with 30 ppm full scale on the logarithmic units and a gain of three (3) on the linear units being the maximum obtainable without amplifier loading.

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7.2.7 SAFElY Due to the low power requirements of the recorder,

one model has been approved for use with Century's line of certified intrinsically safe instruments. m e only difference between the two models is a he.avy blue

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epoxy powder coat on the certified model and different power connector pin arrangement to prevent accidental interchange of the recorders.

7.2.8 MAINTENANCE AND ROUTINE OPERATONS Refer to the manufacturer's (Gulton) manual on the

recorder which is enclosed with each recorder when shipped.

7.28.1 CHANGING CHART SPEEDS The recorder is equipped with a 16 RPM motor which

gives a writing speed of four (4) strikes per second. The chart advance speed is determined by the gear train assembly number used. The inches per hour for each gear train is given in the table on page 9 of the Gulton recorder manual. Refer to the bottom line of the chart adjacent to drive motor 16 and note for example that a number 1 gear train has a chart speed of W'1hour.

a) To change the paper speed. open the recorder, remove gear box spring (on left side). move gear box in direction of arrow on its case and lift out from top. Do not force out from bottom. Iw sen new gear, bottom first. slide into position against arrow direction. Replace gear box spr-

ZERO ADJ. 1

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FIGURE 7-2-1. RECORDER CONTROLS AND ADJUSTMENTS

7.3 ACTIVATED CHARCOAL FILTER ASSEMBLY The Activated Charcoal Filter Assembly, PIN 5100951.

is an optional accessory that can be used with any of the Century portable OVA's. The filter can be installed on the OVA Readout Assembly or attached at the end of the telescoping probe. The filter assembly Is typically filled with activated charcoal which acts as an adsorbent and effectively filters out most non-methane or non- ethane organic vapors. A screw cap on the probe end Is removed for refilling the filter with activated charcoal or any other filtering media desired.

Obtaining a clean air sample for zero baseline check and adjustment on linear OVA's or for a background check on logarithmic OVA's. Running "blank" chromatograms to assess instrument contamination. Rapid screening of methane and non-methane organic vapors. Selective screening for natural gas surveys. As a moisture filter when filled with a desiccant such as silica gel.

A press fit, large adapter on the back of the filter assembly is removed when installing the unit on the telescoping probe. When replacing ::?? cap end after refilling, one wrap of 114 inch teflon tape should be used to seal the threads. The recommended actlvated charcoal for use in the filter is BamebeyCheney, Type GI- 8679.

The life of the filter will depend on the time in use and the concentrations of the compounds being filtered. Under typical industrial air monitoring conditions. the filter will last for many days of continuous sampling.

7.4 OVA SAMPLE DILUTOR An adjustable Sample Dilutor Assembly, PIN 510825

1 , is available as an optional accessory for use on all Century portable Organic Vapor Analyzers. The dilutor may be adjusted over the range of 5:l to W.1 in OVA response. In operation, the dilutor is attached to the end of the telescoping probe or may be connected by external tubing to me input fitting of the OVA side pack case. Dilution of the air being monitored is accompllshed by stream splitting through the use of a needle valve on the sample input. An activated charcoal scrubber is inserted in the main air supply line to the OVA and scrubs the air clean of organic vapors and also creates a slight vacuum at its output side of the scrubber and the vacuum at this point draws the sample air through the needle valve where it mixes with the main air supply g e ing to the OVA detector.

This dilution valve provides a means of sampling vapor levels above the lower explosive level (LEL) and in oxygen deficient atmospheres. These conditlons can occur in normal leak or source survey as the operator gets close to the leak or vapor source or in monitoring various manufacturing or material handling processes. Approximately 14% oxygen is required to sustain operation of the FID in the OVA.

Applications of the filter include: 1)

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7.4.1 SElTlNG DILUTION RATE Prepare-a sample In a bag at a high level;-typically- - -

1 .OOO to 5,000 ppm. Any sultable gas can be used, such as butane from a cigarette lighter: however, a compound simllar to those to be measured provldes greater accuracy. The actual concentration of the gas does not have to be known, since the dllutlon rate Is simply a relative level.

Obtain an OVA reading on the vapor sample with the dllutlon valve removed. Then install the valve, loosen the jam nut and turn the needle valve until the meter reading corresponds to the original reading divided by the dilution factor desired. Retighten the jam nut.

It should be noted that when the dilution valve is used for natural gas leak survey and plnpointlng that the charcoal filter will not remove the methane from the dilution air supply. Care should be taken so that natural gas is not allowed to enter the main air inlet.

7.5 OVA SEPTUM ADAPTER A Septum Adapter, PIN 5106451, is available for direct

on-line sample injection to the GC column inlet. The Septvm Xdzoter rnccn!s C:iec!ly on !he OVA front oanel 9r” z - - ~ ! - .-:act::-: ’ r - 7 n?5 to 2.5 cc mav he made 4 -

using a gas tight syringe. This provides a range of sensitivity-of-approximately lO%-to 1000%-of-the-OVA staw - - dard valve, which has a sample loop volume of approx- lmately 0.25 cc. Syringe injection can cause a flameout; however, the OVA may be reignited after the injection is made. The air in the sample must elute from the column before reignition can be made. The time for the air peak to elute will be a function of the column length and the volume of the sample Injected. For example, a 1 cc sam ple into a 12” column will require waitlng approximately 5 seconds; and, a 2.5 cc sample into a 48” column will require approximately 20 seconds.

The Septum Adapter also provides a means whereby samples can be taken from oxygen deficient atmospheres or process streams and injected directly in- to the chromatograph. Headspace analysis may also be accomplished using the Septum Adapter and a syringe.

When the Septum Adapter Is installed on the OVA, the normal GC sample valve may still be used alternately with the syringe injection. In addition to variable sample size and sensitivity, syringe injections will normally prcb vide greater symmetry and reduced tailing of chromatogram peaks as compared with the standard valve injection.

Unscrew to replace charcoal 7 Readout Adapter

Slip F i t L Teflon Tape on threads

FIGURE 7-3-1. ACTIVATED CHARCOAL FILTER ASSEMBLY

Main A i r Inlet x. - _ _ _ llpm)

ilution Valve

L OVA Telescoping Probe

Jam Nut

Needle Valve. with Wrench Flats 4 6 39

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APPENDIX “A” OVA-I 28

This Appendix includes the following:

Sample forms and typical ApplicationlTech Notes

Side Pack Assy Dwg. No. 510605 Side Pack Assy Parts List N o . LM51OS05

Electronic Component Assy Dwg. No. 510570 Electronic Component Assy Parts List No. LM510570

Cylinder Assy Dwg. No. 510055 Cylinder Assy Parts List No. LM510055

Szhe.na:ic ‘;;icing Ziag:an Svtg. ?:a. 510555

The assembly drawings and parts lists provide loca- tlonlldentif ication information necessary for maintenance, trouble shooting and parts ordering. The drawings are furnlshed only for reference and are subject to Change without notice. The schematic wiring diagram is for use in trouble shooting for possible electronic or wiring problems. Note that components that are not accessible for safety reasons on the certified instruments are not shown on the schematlc. However, typlcal slgnal lsvels at selected polnts are shown.

In using the drawings and parts list to locate items described In the Maintenance Section of this manual, it may flrst be necessary to identify the item in the parts list (by nomenclature), then refer to the corresponding Item number on the drawlng for location.

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CYLINDER A S S Y - = - u a a I u i 3 I EWJS CORP. ARKANSAS CITY. KANSAS I

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SOIL VAPOR SAMPLING PROCEDURES

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Transcript of SOIL VAPOR SAMPLING PROCEDURES